GitHub - aflockofswifts/meetings: Meeting minutes and learnings from the physical space meeting.

A Flock of Swifts

We are a group of people excited by the Swift language. We meet each Saturday morning to share and discuss Swift-related topics.

All people and all skill levels are welcome to join.

2023.10.07

RSVP: https://www.meetup.com/A-Flock-of-Swifts/

2023.09.30

TimeKeep Composable Architecture

We continued the slow development of the TimeKeep app and created our first composable architecture feature.
https://github.com/rayfix/TimeKeep

A feature is a Reducer which contains:

- State
- Action
- Reducer body
- External dependencies injected with @Dependancy

These are buisness logic that are highly configurable and testable. Imagine business logic that can be composed much like views can be composed in SwiftUI.

In SwiftUI, the UI is driven by a Store which consists of a feature in an initial state. The view observes some of all of the state and reduces on it. This is done using a ViewStore. TestStores are special store types that can be used for testing.

Facetime using tvOS

https://support.apple.com/guide/tv/use-facetime-atvb3cced7cd/tvos

Old Man's

https://apps.apple.com/us/app/old-mans/id1473496741

Testing Notifications

Ed told us about many tools you can use to experiment with notifications:

1. Drag an .apns file with notification onto the simulator.
2. xcrun simctl push
3. Use web frontend icloud.developer.com
4. RocketSim

Airpods

Voice isolation is an iOS / MacOS feature.

https://www.macrumors.com/how-to/enable-voice-isolation-cellular-phone-calls/

Other thoughts about Composable Architecture

Side effects. Ray: I am not sure if these are so current.

Vision Pro and Unity

Some discussion about how to get a simple HelloWorld app working with Xcode.

2023.09.23

Swift 5.9 Released

Sites that give you Xcode version and Swift version.

https://swiftversion.net (more swift focused, evolution proposals)
https://xcodereleases.com (more xcode focused, Xcode release notes)

When you open Xcode 15 it gives you this useful link about what's new this year:

https://developer.apple.com/documentation/updates/wwdc2023

Streaming large data files

Some talk about implementing a streaming system.

https://developer.apple.com/documentation/foundation/nsdata/readingoptions

Gestures

Monty was having difficulty with tap and long tap gestures interfering. Some background links to resolve:

Josh's advice was to implement all of the delegate methods and print from there to see how the different gestures are interfering.

https://developer.apple.com/documentation/uikit/uigesturerecognizerdelegate

Monty reported adding this fixed his problem:

func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, 
                       shouldRecognizeSimultaneouslyWith other: UIGestureRecognizer) -> Bool { true }

Keyboard and Toolbars

You can add toolbars to the keyboard since iOS 13.

https://www.hackingwithswift.com/quick-start/swiftui/how-to-add-a-toolbar-to-the-keyboard

    .toolbar {
                ToolbarItemGroup(placement: .keyboard) {
                  if focus {
                    Spacer()
                    Button {
                      focus = false
                    } label: {
                      Text("Done")
                    }
                    .foregroundColor(.white)
                    .buttonStyle(.borderedProminent)
                  }
                }
              }

Conference Report from Frank

This talk on Image Processing was particularly great: https://www.youtube.com/watch?v=yB6kfGwfeXA

Swift Talk at C++Now

https://www.youtube.com/watch?v=lgivCGdmFrw

Tree Data Structures

https://swiftpackageindex.com/search?query=tree+data+structure

TimeKeep App Revisited

We will use the Composable Architecture and create the time keep app:

https://github.com/rayfix/TimeKeep

Next week we will implement a feature.

Swift State Machines

We discussed the presentation by Cory Benfield about state machines: https://www.youtube.com/watch?v=7UC7OUdtY_Q

Some of the key points:

Name the states explicitly with an enum.
Put the enum into a struct and make the state private so you can control how it is initialized.
Make the transitions function calls on the state machine struct. (Avoid huge switch statements.)
Simplify common operations buy using protocols.

Side Journey into The Composable Architecture

Speaking of state machines, the basic components of the composable architecture, "features" are built an awful lot like state machines. We talked about the elements of a TCA feature. You might want to check out their new videos on TCA 1.0. The first one is free. 😉

https://www.pointfree.co/episodes/ep243-tour-of-the-composable-architecture-1-0-the-basics

Core Data

Looking for guidance about where the core data stack should live.

A sample app that uses core data:

https://www.hackingwithswift.com/100/swiftui/53

An example from Josh a while back using core data:

https://github.com/joshuajhomann/Todo

A good way is implement a service and inject with dependency injection:

https://github.com/pointfreeco/swift-dependencies

Controlling the Simulator from the Command Line

https://nshipster.com/simctl/

Learning Swift

The usual answers 😆:

Virtualization and Testing Betas

https://arstechnica.com/gadgets/2022/07/how-to-use-free-virtualization-apps-to-safely-test-the-macos-ventura-betas/

PS: Remember that you can give feedback on broken stuff!

2023.09.09

Trees in Swift

Rainer asked about Replacing (Alamofire)[https://github.com/Alamofire/Alamofire] with URL session. The consensus was to not keep Alamofire unless if you require some feature that it implements that URLSession cannot match such as previously SSL pinning, although Franklin noted that SSL pinning is now implemented on iOS via (App Transport Security)[https://blog.eidinger.info/infoplist-based-certificate-pinning-on-ios].
Peter asked about making a background view interactive while displaying a keyboard on a sheet. Jane suggested, using (Popovers)[https://github.com/aheze/Popovers]. Josh suggested using an environment function to show an arbitrary view from the root view of the app as an overlay.

Josh dived into an extended answer to Ed's question last week about lazy tree traversals in swift. We looked at implementing a tree as an enum with associated types using indirect case to make the associated type storage a reference:

enum Tree<Element> {
    indirect case node(value: Element, children: [Self])
    case leaf(value: Element)
}

let tree = Tree<Int>.node(value: 1, children: [
    .node(value: 2, children: [
        .leaf(value: 4),
        .leaf(value: 5),
        .leaf(value: 6)
    ]),
    .node(value: 3, children: [
        .leaf(value: 7),
        .leaf(value: 8)
    ])
])

Such trees are trivially Codable`` as long as their Elementss are Codable`:

extension Tree: Codable where Element: Codable { }

let encoder = JSONEncoder()
encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
let data = try! encoder.encode(tree)
print(String(data: data, encoding: .utf8)!)

We discussed implementing tree traversals imperatively as a while loop, and implementing them lazily and declaratively as a sequence. We also discussed the difference between breath first traversal and depth first traversal, as being the difference between a using a queue (FIFO) and a stack (LIFO). For real world implementations use a real queue and not an array.

extension Tree {
    var breadthFirstTraversal: some Sequence<Element> {
        sequence(state: [self]) { queue in
            guard !queue.isEmpty else { return nil }
            switch queue.removeFirst() {
            case let .leaf(value): return value
            case let .node(value, children):
                queue.append(contentsOf: children)
                return value
            }
        }
    }
    var depthFirstTraversal: some Sequence<Element> {
        sequence(state: [self]) { stack in
            switch stack.popLast() {
            case let .leaf(value): return value
            case let .node(value, children):
                stack.append(contentsOf: children.reversed())
                return value
            case .none: return nil
            }
        }
    }
}

for value in tree.depthFirstTraversal {
    print(value)
}

An alternative implementation for a binary tree. Note for real world usage binary trees should be implemented as an array to optimize for cache coherency:

enum BinaryTree<Element: Hashable> {
    indirect case node(value: Element, left: Self, right: Self)
    case empty
    static func leaf(_ value: Element) -> Self {
        .node(value: value, left: .empty, right: .empty)
    }
    var isEmpty: Bool {
        switch self {
        case .node: false
        case .empty: true
        }
    }
}

extension BinaryTree {
    var breadthFirstTraversal: some Sequence<Element> {
        sequence(state: [self]) { queue in
            guard !queue.isEmpty else { return nil }
            switch queue.removeFirst() {
            case let .node(value, left, right):
                if !left.isEmpty { queue.append(left) }
                if !right.isEmpty { queue.append(right) }
                return value
            case .empty: return  nil
            }
        }
    }
    var depthFirstTraversal: some Sequence<Element> {
        sequence(state: [self]) { stack in
            switch stack.popLast() {
            case let .node(value, left, right):
                if !right.isEmpty { stack.append(right) }
                if !left.isEmpty { stack.append(left) }
                return value
            case .empty, .none: return  nil
            }
        }
    }
}

let binaryTree = BinaryTree<Int>.node(
    value: 0, 
    left: .node(
        value: 1, 
        left: .leaf(3), 
        right: .leaf(4)
    ),
    right: .node(
        value: 2, 
        left: .leaf(5), 
        right: .leaf(6)
    )
)

2023.09.02

Shader Demo

Josh showed us some amazing code that styles in SwiftUI with metal shader programmers that are dynamically called at runtime. ShapeStyle

Improving Build Times

From iOS Dev weekly:

https://www.manu.show/2023-08-18-improve-build-times-in-spm-packages-and-in-your-apps/

Followup on Decimation Code

Monty was having trouble getting the code to run. Josh used the #Predicate macro in Swift 5.9. A non-macro version looks like this:

let decimation = [
  subviews.indices.lazy.filter { _ in true },
  subviews.indices.lazy.filter { !$0.isMultiple(of: 4) },
  subviews.indices.lazy.filter { !$0.isMultiple(of: 3) },
  subviews.indices.lazy.filter { $0.isMultiple(of: 2) },
  subviews.indices.lazy.filter { $0.isMultiple(of: 3) },
  subviews.indices.lazy.filter { $0.isMultiple(of: 4) },
  subviews.indices.lazy.filter { $0.isMultiple(of: 6) },
  subviews.indices.lazy.filter { _ in false },
]
  let bestFit = decimation.first { indicies in
          zip(indicies, indicies.dropFirst())
              .allSatisfy { left, right in
              frames[left].maxX + minimumSpacing < frames[right].minX
                  }
          }.map(Set.init) ?? []

There were suggestions that he might be running into environment problems. Peter suggested he might want to clean up some of his disk space usage with this Apple Genius recommended application:

https://daisydiskapp.com

Embedded Swift

A Vision document has been released on the Swift forum for using Swift in resource starved environments:

https://forums.swift.org/t/embedded-swift/67057

Keystrokes

Allen was asking about how to get key presses in SwiftUI. There isn't really a good way to do it today but iOS 17 introduces a new modifier described in this article.

https://www.hackingwithswift.com/quick-start/swiftui/how-to-detect-and-respond-to-key-press-events

Modelling Trees

Ed showed us some code he was using to build a tree. There was a suggestion to conform to sequence to allow different traversals. (Breadth first, Depth first) rather than have recursive functions to do the job. He might want

Precise Domain Modelling

We talked about precise domain modelling and making invalid states non-representable. Josh recommended we all watch:

https://www.youtube.com/watch?v=7UC7OUdtY_Q

Learning Swift

The top (and free) choices are

Also, a good resource for getting specific questions answered:

https://join.slack.com/t/swiftcodersla/shared_invite/zt-22cn00k47-KyUe9GQ49GlSazpJ5vifLA

Using C in your Swift

Carlyn found another great example for using C in your Swift code:

https://github.com/apple/swift-nio

2023.08.26

Layout Decimation

We revisited Monty's question about removing views when they are overlapping. Josh presented a solution using the new (Predicate)[https://developer.apple.com/documentation/foundation/predicate] type in Swift 5.7 and a custom SwiftUI Layout. This code can be further optimized by implementing the caching methods on the Layout protocol as we have discussed in previous examples.

import SwiftUI

@Observable
@MainActor
final class ViewModel {
    var items: [Item] = []
    nonisolated init() { }
    func callAsFunction() async {
        let formatter = NumberFormatter()
        formatter.numberStyle = .ordinal
        items = (1...12).compactMap { value in
            formatter.string(for:value).map { string in
                Item(description: string)
            }
        }
    }
}

extension ViewModel {
    struct Item: Identifiable, Hashable, CustomStringConvertible {
        var id: String { description }
        var description: String
    }
}

struct ContentView: View {
    @State private var viewModel = ViewModel()
    var body: some View {
        ProportionalHorizontalLayout {
            ForEach(viewModel.items) { item in
                Text(String(describing: item)).font(.largeTitle)
            }
        }
        .task { await viewModel() }
    }
}

struct ProportionalHorizontalLayout: Layout {
    var minimumSpacing: CGFloat = 10
    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
        proposal.replacingUnspecifiedDimensions(by: .zero)
    }
    func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
        let frames = subviews.enumerated().map { index, view in
            let size = view.sizeThatFits(.unspecified)
            let proportion = Double(index) / Double(max(subviews.count - 1, 1))
            return CGRect(
                origin: .init(
                    x: bounds.origin.x + bounds.width * proportion,
                    y: bounds.origin.y + bounds.midY
                )
                , size: .zero
            )
                .insetBy(dx: -size.width / 2, dy: -size.height / 2)
        }
        
        let decimation = [
            #Predicate { _ in true },
            #Predicate { $0 % 4 != 0 },
            #Predicate { $0 % 3 != 0 },
            #Predicate { $0 % 2 == 0 },
            #Predicate { $0 % 3 == 0 },
            #Predicate { $0 % 4 == 0 },
            #Predicate { $0 % 6 == 0 },
            #Predicate { _ in false }
        ].lazy.compactMap { predicate in
            try? subviews.indices.filter(predicate)
        }

        let bestFit = decimation.first { indicies in
            zip(indicies, indicies.dropFirst()).allSatisfy { left, right in
                frames[left].maxX + minimumSpacing < frames[right].minX
            }
        }.map(Set.init) ?? []

        let nowhere = CGPoint(x: 1e12, y: 1e12)

        for (index, view) in subviews.enumerated() {
            let frame = frames[index]
            view.place(
                at: bestFit.contains(index) ? frame.origin : nowhere,
                anchor: .topLeading,
                proposal: .init(width: frame.size.width, height: frame.size.height)
            )
        }
    }
}

We discussed using closures as an alternative for pre Swift 5.7:

let decimation = [
    subviews.indices.lazy.filter { _ in true },
    subviews.indices.lazy.filter { !$0.isMultiple(of: 4) },
    subviews.indices.lazy.filter { !$0.isMultiple(of: 3) },
    subviews.indices.lazy.filter { $0.isMultiple(of: 2) },
    subviews.indices.lazy.filter { $0.isMultiple(of: 3) },
    subviews.indices.lazy.filter { $0.isMultiple(of: 4) },
    subviews.indices.lazy.filter { $0.isMultiple(of: 6) },
    subviews.indices.lazy.filter { _ in false },
]

Interpolation

We revisited Ed's question from last week about built in Swift methods for linear interpolation. Josh showed an example using both the (mix)[https://developer.apple.com/documentation/accelerate/1425031-mix] function from Swift.Accelerate and the (VectorArithmetic)[https://developer.apple.com/documentation/swiftui/vectorarithmetic] protocol from SwiftUI.

import Combine
import SwiftUI
import simd

import PlaygroundSupport

@Observable
final class ViewModel {
    private(set) var color: Color = .indigo
    var alpha = 0.0
    var method = Method.simd
    enum Method: String, RawRepresentable, Identifiable, CustomStringConvertible, CaseIterable, Hashable {
        case simd, vectorArithmetic, unitPoint
        var id: String { rawValue }
        var description: String { rawValue }
    }
    func onChange(_ colorScheme: ColorScheme) {
        var environmentValues = EnvironmentValues()
        environmentValues.colorScheme = colorScheme
        let s = Color.indigo.resolve(in: environmentValues)
        let d = Color.orange.resolve(in: environmentValues)
        switch method {
        case .simd:
            let indigioRGBA = SIMD4(s.red,  s.green,  s.blue,  s.opacity)
            let orangeRGBA = SIMD4(d.red,  d.green, d.blue,  d.opacity)
            let rgba = mix(indigioRGBA, orangeRGBA, t: Float(alpha))
            color = Color(red: Double(rgba.x), green: Double(rgba.y), blue: Double(rgba.z), opacity: Double(rgba.w))
        case .vectorArithmetic:
            self.color = Color(
                red: Double(s.red.interpolated(towards: d.red, amount: alpha)),
                green: Double(s.green.interpolated(towards: d.green, amount: alpha)),
                blue: Double(s.blue.interpolated(towards: d.blue, amount: alpha)),
                opacity: Double(s.opacity.interpolated(towards: d.opacity, amount: alpha))
            )
        case .unitPoint:
            let t = UnitCurve.easeInOut.value(at: alpha)
            self.color = Color(
                red: Double(s.red.interpolated(towards: d.red, amount: t)),
                green: Double(s.green.interpolated(towards: d.green, amount: t)),
                blue: Double(s.blue.interpolated(towards: d.blue, amount: t)),
                opacity: Double(s.opacity.interpolated(towards: d.opacity, amount: t))
            )
        }
    }
}

struct V: View {
    @State private var viewModel = ViewModel()
    @Environment(\.colorScheme) var colorScheme
    var body: some View {
        Picker("Method", selection: $viewModel.method) {
            ForEach(ViewModel.Method.allCases) { method in
                Text(String(describing: method)).tag(method)
            }
        }
        .pickerStyle(.segmented)
        Slider(value: $viewModel.alpha)
        Circle()
            .fill(viewModel.color)
            .onChange(of: viewModel.alpha) { _, _ in viewModel.onChange(colorScheme) }
            .onChange(of: colorScheme) { _, _ in viewModel.onChange(colorScheme) }
            .onChange(of: viewModel.method) { _, _ in viewModel.onChange(colorScheme) }
    }
}

let v = V()
PlaygroundPage.current.setLiveView(V())

ShapeStyle continued

Josh continued discussion of shape style and the new (Shader)[https://developer.apple.com/documentation/swiftui/shader] conformance in iOS 17 as well as the new (visualEffect)[https://developer.apple.com/documentation/swiftui/visualeffect?changes=_6] modifier. We also touched on how shader makes use of the String verison of (@dynamicMemberLookup)[https://github.com/apple/swift-evolution/blob/main/proposals/0195-dynamic-member-lookup.md] and (@dynamicCallable)[https://github.com/apple/swift-evolution/blob/main/proposals/0216-dynamic-callable.md].

2023.08.19

CardView

We went on a random walk to create a CardView in SwiftUI. Some key learnings:

Alignment can give better performance using Spacer().
Use shapeStyle and semantic colors to make dark mode work well.
You can use @Environment(\.colorScheme) var colorScheme to do special things for .dark vs .light mode.

import SwiftUI

struct CardView<Content: View>: View {
  let size: Double
  let title: String
  let subtitle: String
  let isSelectable: Bool
  let isSelected: Bool
  let isLiked: Bool
  let radius = 10.0
  @ViewBuilder var content: () -> Content
  
  @Environment(\.colorScheme) var colorScheme
  
  private var shadowColor: Color {
    colorScheme == .dark ?
    Color(red: 0.3, green: 0.3, blue: 0.3).opacity(0.8) :
    Color(red: 0.9, green: 0.9, blue: 0.9).opacity(0.8)
  }
  
  var body: some View {
    ZStack {
      Rectangle().foregroundStyle(.background)
      content()
        .padding(10)
        .aspectRatio(contentMode: .fit)
      VStack(alignment: .leading) {
        Spacer()
        HStack {
          VStack(alignment: .leading) {
            HStack(alignment: .firstTextBaseline) {
              Text(title).bold(); Spacer();
              Image(systemName: "heart.fill").foregroundColor(.red)
                .opacity(isLiked ? 1 : 0)
            }
            Text(subtitle).font(.caption)
          }
          Spacer()
        }
        .padding()
        .frame(width: size)
        .background(Rectangle().foregroundStyle(.bar))
      }
    }
    .overlay(alignment: .topTrailing) {
      Image(systemName: "checkmark.circle.fill")
        .font(.title)
        .symbolRenderingMode(.multicolor)
        .foregroundStyle(.white, .blue)
        .padding(10)
        .opacity(isSelectable ? 1 : 0)
    }
    .frame(width: size, height: size)
    .cornerRadius(radius)
    .shadow(color: .secondary,
            radius: radius)
  }
}

struct ContentView: View {  
  var body: some View {
    CardView(size: 230,
             title: "Around the world",
             subtitle: Date.now.formatted(),
             isSelectable: false,
             isSelected: true,
             isLiked: true) {
      Image(systemName: "globe").resizable()
    }
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}

Infinite Loop Bug

Franklin posed this question:

https://stackoverflow.com/questions/76902789/how-can-i-fix-screen-freezing-and-excessive-cpu-usage-when-attempting-to-impleme/76904182#76904182

Josh showed that the problem could be fixed making @ObservedObject into @StateObject. Also:

    final class MyBadClass {
        init() {
            logger.log("\(String(describing: Self.self)) \(#function)")
        }
    }
    
    struct MyBadClassEnvironmentKey: EnvironmentKey {
        static let defaultValue: MyBadClass = .init()
        typealias Value = MyBadClass
    }
    
    extension EnvironmentValues {
        var expensive: MyBadClass {
            self[MyBadClassEnvironmentKey.self]
        }
    }
    
    
    final class Test: ObservableObject {
        init() {
            logger.log("\(String(describing: Self.self)) \(#function)")
        }
    }

Swift C++ Integration

In Swift, you can construct a Swift C++ std::string with the code std.string(swiftString)

Activity Classification

Bill wanted an outline of how to do activity classification. Josh provided a quick explanation but there is a WWDC 2019 presentation about the very topic:

https://developer.apple.com/wwdc19/426

Interpolation

Ed working on a simple interpolation algorithm for an (Ordered) dictionary. It probably works fine for what he wants it to do but might want to check out a more exhaustive solution (that uses SIMD):

https://developer.apple.com/documentation/accelerate/2896707-simd_mix

Stanford 2023

From Hegarty

https://cs193p.sites.stanford.edu/2023

Animations

You can do it at the website now:

https://www.lottielab.com/dashboard

2023.08.12

ShapeStyle

Josh put together an epic dmeo project to demostrate the many capabilities of ShapeStyle in SwiftUI. Link TBD.

Project IDX

A new development enviornment for full stack developers by google. https://idx.dev

[Ray: Go, Flutter, JS Python. Swift not even on the coming-soon list. 😅]

Bluetooth

Rainer wondering about the security of a temperature sensor. The main risk is the actual app.

Frank notes: For reverse engineering: Lightblue and BluefruitConnect (iPhone apps) can do the job.

You can write your own App! CoreBluetooth.

https://github.com/jeradesign/BluetoothDump (example from John Brewer)
https://github.com/joshuajhomann/bluetooth (example from Josh Homann)

A package that can make it easier to handle data according to Frank:

https://swiftpackageindex.com/QuickBirdEng/DataKit

Question: Reference copying

var a = someClass
a = someClass.parent

The a is simply a referece that points to the same underlying object that someClass points to. What a references changes but the type itself is not mutated in this short example.

C++ Interop

A cool set of links from carlyn who is exploring this for USD.

Also (work-in-progress):

2023.08.05

Result Builder Exploration

https://gist.github.com/carlynorama/3e6765d4a87aaaf3fe2f69abb14764ca

Actors in Action

protocol PersistenceServiceProtocol: Actor {
   func create(timestamp: Date)  throws -> Item
   var count: Int { get throws }
   ...
}

This enforces actor semantics for conformance to the protocol. You don't have to add async everywhere even though methods can still suspend.

Centering Text and Circle

Presented by Monty. The problem is that you want to center the view at the center of the circle and have the text above it. Here is the solution we arrived at:

 struct CircleView: View {
   var body: some View {
     Circle()
       .fill(.yellow)
       .frame(width: 40, height: 40)
       .overlay(
         Text("Yellow").fixedSize().offset(y: -40), 
         alignment: .bottom)    
    }
}

Some notes:

Overlay keeps the Circle anchor at the center.
fixedSize() removes text clipping
A more general solution that was covered previously: https://github.com/joshuajhomann/Wordle/blob/main/Wordle/AnchorToParentLayout.swift

Conferences and meetings

https://s2023.siggraph.org/ (This week!)
iosdevhappyhour.slack.com
ios-developers.slack.com

License for command line tools

Bob notes:

sudo xcodebuild -license

Using Reflection with Binding

An extended example from Ed. We didn't figure it out during the meeting but Ed sent in the answer shortly after:

import SwiftUI
import Combine
import PlaygroundSupport

struct M {
  var a : Double?
  var b : Double?
  
  static var props : [String] {
    let mirror = Mirror(reflecting: M().self)
    return mirror.children.compactMap { $0.label }
  }
}

struct R {
  var n : String
  var r : Double?
  func good() -> Bool {
    r != nil && r! >= 2 && r! <= 3
  }
}

class List : ObservableObject {
  @Published var r : [R]
  
  init() {
    let props = M.props
    self.r = props.enumerated().map { i,p in
      R(n: p, r: nil)
    }
  }
}


struct BView : View {
  @StateObject private var list = List()
  var body: some View {
    VStack {
      ForEach($list.r.indices, id:\.self) { i in
        TextField(value: $list.r[i].r, format: .number, label: {Text(list.r[i].n)})
          .textFieldStyle(.roundedBorder)
          .padding()
          .background(
            RoundedRectangle(cornerRadius:10.0)
              .fill(list.r[i].good() ? Color.green : Color.clear)
          )
      }
    }
  }
}

let view = BView()
PlaygroundPage.current.setLiveView(view)

Apple Watches

New ones are coming so you may want to wait for a price drop or the new model.

https://www.apple.com/shop/product/MPA13AM/A/41mm-midnight-braided-solo-loop-size1

The Composable Architection 1.0

Released this week.

https://pointfreeco.github.io/swift-composable-architecture/main/tutorials/meetcomposablearchitecture/

VisionPro Meetup

Don't forget!

https://www.meetup.com/vision-pro-developers/events/294299473/

2023.07.29

Puyo Puyo app

Josh finished the Puyo Puyo app (code here)[https://github.com/joshuajhomann/PuyoPuyo]

Timers

Talked about timers and how to invalidate them. Some live code from Josh:

import SwiftUI
import UIKit
import PlaygroundSupport
    
    
let timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: false) { _ in
    print(timer)
}
    
timer.invalidate()

Some resources:

Also, consider using a timeline view:

https://developer.apple.com/documentation/swiftui/timelineview

Getting a Preview in Playground

import SwiftUI
import UIKit

import PlaygroundSupport


struct V: View {
    var body: some View {
        Color.red
    }
}
    
PlaygroundPage.current.setLiveView(V())

Blog Posting

Many options and opinions here.

GitHub Pages
Publish (all Swift and neat, but not designed for general usage)
https://micro.blog
Substack
https://getgrav.org
https://www.nearlyfreespeech.net
https://www.netlify.com
https://gohugo.io

USD

Carlyn talks about her exploration with the USD file format.

https://www.whynotestflight.com/excuses/hello-usd-part-16-swift-just-sipping-openusd-through...-a-pipe/

2023.07.22

Discussion about CI

GitHub Actions
https://developer.apple.com/xcode-cloud/

Getting and Setting Colors

Monty had a question about getting the hue, saturation, and brightness from a SwiftUI Color that he had already set.

Josh used a playground to demonstrate the relationship between SwiftUI colors, CGColors, and UIColor. Some serious API archeology happening here! 😄

import SwiftUI
import UIKit
import PlaygroundSupport
    
    
let swiftuiColor = Color(hue: 0.668944, saturation: 1.0, brightness: 0.267304)
let cgColor = swiftuiColor.cgColor
let uiColor = UIColor(cgColor: cgColor!)
    
var (h,s,v,a) = (CGFloat.zero,CGFloat(1.0),CGFloat(1.0),CGFloat(1.0))
    
print(uiColor.getHue(&h, saturation: &s, brightness: &v, alpha: &a))
    
print(h,s,v,a)

Weather API

Another question Monty had was about using WeatherKit to get sunrise and sunset. You can use wheter kit to do this with SunEvents.

You can also use a free API:

https://sunrise-sunset.org/api

You can do your own "cleanroom" implementation that can be computed locally.

Vision Pro

Unity beta release. A good article that explains what is possible with the different modes (RealityKit vs Unity)

https://arstechnica.com/gadgets/2023/07/unity-launches-visionos-beta-opening-the-doors-for-existing-apps-and-games/

Ad Hoc Database

Ed took us on a journey about using dictionaries to implement fast lookup to a local database.

We talked about everything from sets to the demise of C-style for loops.

Puyopuyo Continued

Josh continued his epic example creating Puyo puyo in iOS17 SwiftUI, which will probably complete next week with the collapse of puyo towers! 😂

2023.07.15

New HTTP Types

JSON Schema

https://json-schema.org

A project that uses JSON Schema

https://www.swift.org/blog/introducing-swift-openapi-generator/

Universal Scene Description Demo

Carlyn is implementing the USD format from scratch in Swift. You can find a flurry of blog posts on her blog: https://www.whynotestflight.com

She showed this JavaScript library that does similar thing to what she wants to do: https://p5js.org

A big part of the library is using ResultBuilder. Josh did a presentation on this last year. This is his template

@resultBuilder
    struct <#Name#>Builder {
        typealias Expression = <#Expression#>
        typealias Component = <#Component#>
        typealias FinalResult = <#FinalResult#>
    
        static func buildBlock(_ components: Component...) -> Component {
            buildArray(components)
        }
        static func buildExpression(_ expression: Expression) -> Component {
    
        }
        static func buildOptional(_ component: Component?) -> Component {
            component ?? <#empty#>
        }
        static func buildEither(first component: Component) -> Component {
            component
        }
        static func buildEither(second component: Component) -> Component {
            component
        }
        static func buildArray(_ components: [Component]) -> Component {
    
        }
        static func buildLimitedAvailability(_ component: Component) -> Component {
            component
        }
        static func buildFinalResult(_ component: Component) -> FinalResult {
    
        }
    }

Migratable Codable

Ed had some discussion on making codable formats that can migrate. Here is code from Josh proposed:

final class A {
        var integer: Integer
        init(dictionary: [Swift.String: Any]) {
            integer = .init(dictionary: dictionary.compactMapValues { $0 as? Int})
        }
        @dynamicMemberLookup
        struct Integer {
            var dictionary: [Swift.String: Int]  
            subscript(dynamicMember member: Swift.String) -> Int {
                dictionary[member] ?? 0
            }
        }
        @dynamicMemberLookup
        struct String {
            var dictionary: [Swift.String: Swift.String]  
            subscript(dynamicMember member: Swift.String) -> Swift.String {
                dictionary[member] ?? ""
            }
        }
}
    
let a = A(dictionary: ["a": "a", "b": 1])
print(a.integer.b)

Puyopuyo

The demo continues showing, custom Layout, animation, state management, and more.

2023.07.08

Working with Autolayout and Size Classes

Emil Safier gave a talk a few years back: https://youtu.be/Hao5mA-sQbQ

Swiftful YouTube

Humberto De La Cruz recommends a video series on YouTube called "Swiftful Thinking".

Vision Pro

Remember there is a meetup group starting this Tuesday.

https://www.meetup.com/vision-pro-developers/

    #if os(xrOS)
      let minWidthX: CGFloat = 300
    #else
      let minWidthX = UIScreen.main.bounds.width
    #endif

Best Monitor to Buy

Various suggestions from people.

How to Understand a Big Codebase

Understand the dependencies.
ASK Questions!
Find out what the intent is.
ASK Questions!

PuyoPuyo, Animation, Layout

An epic example of how to do custom layout.

Code: TBD.

2023.07.01

Welcome Monty

New to iOS programming. Currently doing a UDEMY course but several people say he would be better off doing 100 days of SwiftUI.

Discussed his passion project: calendar app for cognitively impaired. Some advice:

Try out SwiftUI
Draw out your UI on paper
100 days of SwiftUI https://www.hackingwithswift.com/100/swiftui
Guided Access https://support.apple.com/guide/ipad/guided-access-ipada16d1374/ipados
Apps to reference: https://9to5mac.com/2022/09/28/up-ahead-countdown-app-iphone/

Tutorial: https://devtut.github.io/ios/eventkit.html

Realm and Mongo Atlas

https://atlasmadness.devpost.com
https://en.wikipedia.org/wiki/MongoDB_Inc
https://aws-quickstart.github.io/quickstart-mongodb-atlas/ — notes a three-node cluster minimum for a replica set for high availability, but it does not say it must be replicated across regions.

Layout Problems with Geometry Reader

Mark trying to make a list that can control row spacing. Attempts at using GeometryReader seemed to break lineLimit modifiers. He tried putting the GeometryReader in the overlay but it didn't help. Brainstorm advice was to not use List (and implement Edit functionality) or to use Layout.

PDF Multipage on Mac

https://www.hackingwithswift.com/quick-start/swiftui/how-to-render-a-swiftui-view-to-a-pdf

visionPro Meetup

New meetup to start July 11, 2023. Online and in-person.

https://www.meetup.com/vision-pro-developers/

2023.06.24

Whats new in animation for iOS 17

Download the project here

2023.06.17

Curve continuity

Josh discussed Squircles and C1 continuity and saw how the squircle differs from a rounded rect:

import SwiftUI
import PlaygroundSupport

struct V: View {
    var body: some View {
        RoundedRectangle(cornerRadius: 250, style: .circular)
            .fill(.yellow)
            .overlay(
                RoundedRectangle(cornerRadius: 250, style: .continuous)
                    .fill(.blue.opacity(0.5))
            )
            .aspectRatio(1, contentMode: .fill)
            .padding()
    }
}

PlaygroundPage.current.setLiveView(V())

Changes to timing animation timing functions in iOS 17

Josh went through a project demonstrating the new spring functions in iOS 17 https://github.com/joshuajhomann/AnimationCurves

2023.06.10

WWDC Roundup

We talked about what we thought was cool from WWDC. This site collects notes from WW.

https://wwdcnotes.com/events/wwdc23/

Some Favorite features:

TipKit (works with UIKit too)
Macros (and all they enable)
Xcode Documentation Previews
Widgets, Siri Integration, Intents
Logging Console in Xcode
Better autocompletion
Improvements to scroll views
Sensitive Content Analysis

Josh is worried about how the new Observation feature in SwiftUI works with testing.

Vision Pro

Cool New Presentation Software

https://ia.net/presenter

2023.06.03

WWDC is next week! some community event links:

Lab registration:

https://developer.apple.com/wwdc23/labs-and-activities/dashboard/upcoming/activities/register

Demo: detecting leaks in your app

github project: Leak Detector

2023.05.27

Primary associatedtypes, existentials and opaque types: why you should care With a type that has primary associatedtypes we can use the existential any to erase the type at the contract level:

struct Item { }
	
	protocol Repository {
	    func getItems() -> any Publisher<[Item], Never>
	}
	
	
	final class EmptyRepository: Repository {
	    func getItems() -> any Publisher<[Item], Never> {
	        Just([])
	    }
	}
	
	
	final class NeverRepository: Repository {
	    func getItems() -> any Publisher<[Item], Never> {
	        Empty(completeImmediately: false)
	    }
	}

But if we try the same thing with the opaque type it doesn't work because the compiler cannot infer a single concrete type for some Publisher<Item, Never>

	protocol Repository {
        // This doesn't compile
	    func getItems() ->  some Publisher<[Item], Never>
	}
	
	
	final class EmptyRepository: Repository {
	    func getItems() -> some Publisher<[Item], Never> {
	        Just([])
	    }
	}

The solution is to use a generic:

	protocol Repository {
	    associatedtype GetItemPublisher: Publisher<[Item], Never>
	    func getItems() -> GetItemPublisher
	}
	
	
	final class EmptyRepository: Repository {
	    func getItems() -> some Publisher<[Item], Never> {
	        Just([])
	    }
	}
	
	
	final class NeverRepository: Repository {
	    func getItems() -> some Publisher<[Item], Never> {
	        Empty(completeImmediately: false)
	    }
	}

While either the existential or the associatedtype + opaque type work for types with primary associatedtypes like Publisher, only the associatedtype + opaque type works for types without primary associatedtypes like AsyncSequence:

protocol AsyncRepository<Element> {
	    associatedtype Element
	    associatedtype GetItemAsyncSequence: AsyncSequence where GetItemAsyncSequence.Element == Element
	    func getItems() -> GetItemAsyncSequence
	}
	
	struct AsyncEmptyRepository: AsyncRepository {
	    typealias Element = [Item]
	    func getItems() -> AsyncPrefixSequence<AsyncStream<[Item]>> {
	        AsyncStream { [] }.prefix(1)
	    }
	}
	
	struct AsyncNeverRepository: AsyncRepository {
	    typealias Element = [Item]
	    func getItems() -> AsyncStream<[Item]> {
	        AsyncStream { nil }
	    }
	}

Stagemanger on the simulator

simctl: https://nshipster.com/simctl/
using simclt to enable stage manager xcrun simctl spawn booted defaults write -g SBChamoisWindowingEnabled -bool true :https://developer.apple.com/forums/thread/708567
open the HIG in Xcode: shift + cmd + H

demo project: switching between SplitView and TabView based on iPadOS window size:

import SwiftUI

struct ViewSizeEnvironmentKey: EnvironmentKey {
    static var defaultValue: CGSize = .zero
}

extension EnvironmentValues {
    var viewSize: CGSize {
        get { self[ViewSizeEnvironmentKey.self] }
        set { self[ViewSizeEnvironmentKey.self] = newValue }
    }
}

struct MeasureModifier: ViewModifier {
    let alignment: Alignment
    func body(content: Content) -> some View {
        GeometryReader { proxy in
            content
                .environment(\.viewSize, proxy.size)
                .frame(width: proxy.size.width, height: proxy.size.height, alignment: alignment)
        }
    }
}

extension View {
    func measure(alignment: Alignment = .center) -> some View {
        modifier(MeasureModifier(alignment: alignment))
    }
}

@MainActor
final class ViewModel: ObservableObject {
    @Published var selectedTab: String
    @Published var selectedItem: String?
    let items = ["star", "circle", "checkmark"]
    init() {
        selectedTab = items[0]
        selectedItem = items[0]
        $selectedTab.removeDuplicates().map { $0 as String? }.assign(to: &$selectedItem)
        $selectedItem.removeDuplicates().compactMap { $0 }.assign(to: &$selectedTab)
    }
}

enum Platform {
#if os(macOS)
    static let isMac = true
#else
    static let isMac = false
#endif
}

struct RootView: View {
    @StateObject private var viewModel = ViewModel()
    @Environment(\.viewSize) private var viewSize
    @Environment(\.horizontalSizeClass) private var horizontalSizeClass
    @Environment(\.verticalSizeClass) private var verticalSizeClass
    var body: some View {
        if viewSize.width > 750 || Platform.isMac {
            NavigationSplitView {
                List(viewModel.items, id: \.self, selection: $viewModel.selectedItem) { item in
                    Image(systemName: item)
                }
                .listStyle(.sidebar)
            } detail: {
                content(for: viewModel.selectedItem)
            }

        } else {
            TabView(selection: $viewModel.selectedTab) {
                ForEach(viewModel.items, id: \.self) { item in
                    content(for: item)
                        .tabItem { Image(systemName: item) }
                        .tag(item)
                }
            }
        }
    }

    func content(for item: String?) -> some View {
        VStack {
            Label(item ?? "no selection", systemImage: item ?? "").font(.largeTitle)
            Text(String(describing: horizontalSizeClass))
            Text(String(describing: verticalSizeClass))
        }
    }
}

struct ContentView: View {
    var body: some View {
        RootView().measure()
    }
}

2023.05.20

Followups from Rainer

Two line buttons don't work well. Instead he needed to use a view with a tap gesture and was able to put it in nested scroll views.
Looking at using a base class and derived class instead of a protocol with associated types. Josh warned him it might not be as good as sticking with a protocol.
Using transform compositions to translate and rotate points.

Transitions From Ed

Rather than using transitions mentioned last week, Ed pursued another solution. We worked on it together to simplify how it ran.

Some notes:

import SwiftUI

struct BackImage: View {
  let index: Int
  let size: CGSize
  @State var opacity = 0.0
  var x: Double {
    Double.random(in: 0..<1) * size.width - 60.0
  }
  var y: Double {
    Double.random(in: 0..<1) * size.height - 60.0
  }
  var delay: TimeInterval {
    0.001 * Double(index)
  }
  var body: some View {
    Image(systemName: "star.fill")
      .resizable()
      .foregroundColor(index.isMultiple(of: 2) ? .blue : .yellow)
      .frame(width: 120, height: 120)
      .offset(x: x, y: y)
      .opacity(opacity)
      .animation(.easeIn.delay(delay).speed(0.25),
                 value: opacity)
      .task {
        opacity = 1
      }
  }
}

struct BackView: View {
  var body: some View {
    GeometryReader { proxy in
      ForEach(0..<250, id: \.self) { index in
        BackImage(index: index, size: proxy.size)
      }
    }
  }
}

Discussion about Tasks

New Swift Project Structure

Core team is still at the top with new Steering Groups and Workgroups.

https://www.swift.org/blog/evolving-swift-project-workgroups/

A Great Tutorial for The Composable Architecture

Uses the Xcode tutorial format and explains The Composable Architecture.

https://pointfreeco.github.io/swift-composable-architecture/main/tutorials/meetcomposablearchitecture

The tutorial technology is also interesting:

Macros are coming in Swift 5.9

Kawasumi build an macro expression library called PowerAssert.

Type Erasure

We taked about Type Erasure and opening existentials.

https://forums.swift.org/t/understanding-the-limitations-of-open-existential/65022/3

2023.05.13

Bard and Pong

Josh tested out Google's AI Bard to make the game Pong. The result kind of worked but was a little bit dicey in how it tried to render the view.

ChatGPT seems to be better at writing Swift code at the moment but be sure to use 4, otherwise you get older, less idiomatic Swift.

Representing an optional as an array

import Foundation
	
let a: Int? = nil
	
extension Optional {
    var asArray: [Wrapped] {
        map { [$0] } ?? []
    }
}
print(a.asArray)

Another alternative (TMTOWTDI):

[b].compactMap { $0 }

This approach is more "compact" (haha) but can require two allocations where the first way is always a single allocation.

Identifiable

Watch out that you don't have duplicate IDs or you will confuse the pants off of SwiftUI.

Wheel of Fortune Demo

Josh created a Wheel of Fortune using SwiftUI drawing groups for performance. Rotations effect applied do the magic of creating wedges in the proper place and spinning the wheel.

final class WheelViewModel: ObservableObject {
    @Published private(set) var items: [Item] = []
    @Published private(set) var angle: Angle = .zero
    @Published private(set) var winner = ""
    private let names: [String]
    private var winningIndex = 0
    let arcLength: Double
    init() {
        let colors: [UIColor] = [#colorLiteral(red: 0.8039215803, green: 0.8039215803, blue: 0.8039215803, alpha: 1), #colorLiteral(red: 0.9058823529, green: 0.9058823529, blue: 0.9058823529, alpha: 1), #colorLiteral(red: 0.6434109211, green: 0.625438869, blue: 0.6250535846, alpha: 1),]
        let url = Bundle.main.url(forResource: "list", withExtension: "csv")
        let data = try! Data(contentsOf: url!)
        let text = String(data: data, encoding: .utf8)!
        names = text
            .components(separatedBy: .newlines)
            .filter { !$0.isEmpty }
            .lazy
            .map { $0.localizedCapitalized }
            .reduce(into: Set<String>()) { $0.insert($1) }
            .sorted(by: <)
        let count = Double(names.count)
        arcLength = (2 * .pi) / count
        items = names
            .enumerated()
            .map { offset, name in
                .init(
                    name: name.description,
                    color: Color(uiColor: colors[offset % colors.count]),
                    rotation: .radians(Double(offset) * arcLength - 0.5 * .pi)
                )
            }
    }

    func tap() {
        winningIndex = names.indices.randomElement() ?? 0
        let remainder = fmod(angle.radians, 2.0 * .pi)
        let revolutions = 2 * 2.0 * .pi + angle.radians
        angle = .radians(revolutions - remainder - Double(winningIndex) * arcLength)
        print("Winner: \(names[winningIndex])")
    }

    func showWinner() {
        winner = names[winningIndex]
    }

    struct Item: Identifiable {
        var id: String { name }
        var name: String
        var color: Color
        var rotation: Angle
    }
}

struct Wedge: View {
    var title: String
    var color: Color
    var arcLength: Angle
    var bounds: CGRect
    var body: some View {
        ZStack(alignment: .center) {
            let center = CGPoint(x: bounds.midX, y: bounds.midY)
            let radius = bounds.width / 2
            let halfArcLength = Angle.radians(arcLength.radians * 0.5)
            Path { path in
                path.move(to: center)
                path.addArc(
                    center: center,
                    radius: radius,
                    startAngle: -halfArcLength,
                    endAngle: halfArcLength,
                    clockwise: false
                )
                path.closeSubpath()
            }
            .foregroundColor(color)
            Text(title)
                .offset(x: bounds.width / 3)
                .position(x: bounds.midX, y: bounds.midY)
        }
    }
}

struct Wheel: View {
    @StateObject private var viewModel: WheelViewModel = .init()
    var body: some View {
        ZStack {
            GeometryReader { proxy in
                let bounds = proxy.frame(in: .local)
                ZStack(alignment: .center) {
                    ForEach(viewModel.items) { item in
                        Wedge(title: item.name, color: item.color, arcLength: .radians(viewModel.arcLength), bounds: bounds)
                            .rotationEffect(item.rotation)
                    }
                }
            }
            .drawingGroup()
            .padding()
            .rotationEffect(viewModel.angle)
            GeometryReader { proxy in
                let bounds = proxy.frame(in: .local)
                Wedge(
                    title: "",
                    color: .cyan.opacity(0.5),
                    arcLength: .radians(viewModel.arcLength),
                    bounds: bounds
                )
                    .rotationEffect(-.radians(0.5 * .pi))
                    .blendMode(.sourceAtop)
            }
        }
        .aspectRatio(1, contentMode: .fit)
        .onTapGesture {
            withAnimation(.easeInOut(duration: 8)) {
                viewModel.tap()
            }
        }
    }
}

PlaygroundPage.current.setLiveView(Wheel().frame(width: 800, height: 800))

2023.05.06

Mojo from Chris Lattner

It is like Python++

https://www.fast.ai/posts/2023-05-03-mojo-launch.html

Upcoming Conferences

Spiral Example

Josh created a epic spiral example and blew our minds with maximum irrationality. (ϕ)

Repo: TBD

2023.04.29

Frank showed how to use NSViewRepresentable to control window zooming on macOS with SwiftUI

//
	//  NSWindowDemoApp.swift
	//  NSWindowDemo
	//
	//  Created by Frank Lefebvre on 15/04/2023.
	//
	
	import SwiftUI
	import AppKit
	
	@main
	struct NSWindowDemoApp: App {
	    let imageWidth = 800.0
	    let imageHeight = 600.0
	    
	    var body: some Scene {
	        Window("Image", id: "main") {
	            ContentView()
	                .windowSize(idealWidth: imageWidth, idealHeight: imageHeight)
	        }
	    }
	}
	
	struct WindowAccessor: NSViewRepresentable {
	    let callback: (NSWindow) -> Void
	    
	    private class WindowDetectingView: NSView {
	        private let callback: (NSWindow) -> Void
	        
	        init(_ callback: @escaping (NSWindow) -> Void) {
	            self.callback = callback
	            super.init(frame: .zero)
	        }
	        
	        required init?(coder: NSCoder) {
	            fatalError("init(coder:) has not been implemented")
	        }
	        
	        override func viewDidMoveToWindow() {
	            if let window {
	                DispatchQueue.main.async {
	                    self.callback(window)
	                }
	            }
	        }
	    }
	    
	    func makeNSView(context: Context) -> some NSView {
	        WindowDetectingView(callback)
	    }
	    
	    func updateNSView(_ nsView: NSViewType, context: Context) {
	    }
	}
	
	extension View {
	    func windowSize(idealWidth: CGFloat, idealHeight: CGFloat) -> some View {
	        modifier(WindowSizeModifier(idealWidth: idealWidth, idealHeight: idealHeight))
	    }
	}
	
	struct WindowSizeModifier: ViewModifier {
	    let idealWidth: CGFloat
	    let idealHeight: CGFloat
	    @State private var zoomDelegate: WindowZoomDelegate?
	    
	    func body(content: Content) -> some View {
	        content
	            .background(WindowAccessor(callback: { window in
	                if window.styleMask.contains(.fullSizeContentView) {
	                    let savedFrame = window.frame
	                    window.styleMask.remove(.fullSizeContentView)
	                    window.setFrame(savedFrame, display: false)
	                }
	                update(window: window, idealWidth: idealWidth, idealHeight: idealHeight)
	                zoomDelegate = WindowZoomDelegate(idealWidth: idealWidth, idealHeight: idealHeight, window: window)
	                window.delegate = zoomDelegate
	            }))
	    }
	    
	    private func update(window: NSWindow, idealWidth: CGFloat, idealHeight: CGFloat) {
	        window.contentAspectRatio = .init(width: idealWidth, height: idealHeight)
	    }
	}
	
	final class WindowZoomDelegate: NSObject, NSWindowDelegate {
	    let idealWidth: CGFloat
	    let idealHeight: CGFloat
	    private weak var window: NSWindow?
	    private weak var target: NSWindowDelegate?
	    
	    init(idealWidth: CGFloat, idealHeight: CGFloat, window: NSWindow) {
	        self.idealWidth = idealWidth
	        self.idealHeight = idealHeight
	        self.window = window
	        self.target = window.delegate
	        super.init()
	    }
	    
	    func windowWillUseStandardFrame(_ window: NSWindow, defaultFrame newFrame: NSRect) -> NSRect {
	        guard let screenFrame = window.screen?.visibleFrame, let contentFrame = window.contentView?.frame else { return newFrame }
	        let proposedContentRect = window.contentRect(forFrameRect: newFrame)
	        let newWidth = min(idealWidth, proposedContentRect.width)
	        let newHeight = min(idealHeight, proposedContentRect.height)
	        var newOrigin = window.frame.origin
	        let offset = contentFrame.height - newHeight
	        newOrigin.y += offset
	        newOrigin.y = max(newOrigin.y, screenFrame.minY)
	        return window.frameRect(forContentRect: NSRect(x: newOrigin.x, y: newOrigin.y, width: newWidth, height: newHeight))
	    }
	    
	    override func responds(to aSelector: Selector!) -> Bool {
	        Self.instancesRespond(to: aSelector) || (target?.responds(to: aSelector) ?? false)
	    }
	    
	    override func forwardingTarget(for aSelector: Selector!) -> Any? {
	        target
	    }
	}
}

Josh showed a similar playground using UIViewRepresentable and the UIResponder chain to walk up the chain and mutate a UIKit type from within SwiftUI:

import UIKit
import SwiftUI
import PlaygroundSupport

struct ProxyView: UIViewRepresentable {
    var onMoveToWindow: (UIView) -> Void
    func makeUIView(context: Context) -> Proxy { .init() }
    func updateUIView(_ proxy: Proxy, context: Context) {
        proxy.onMoveToWindow = onMoveToWindow
    }
    final class Proxy: UIView {
        var onMoveToWindow: ((UIView) -> Void)?
        override func didMoveToWindow() {
            super.didMoveToWindow()
            guard window != nil else { return }
            backgroundColor = .clear
            onMoveToWindow?(self)
        }
    }
}

extension View {
    func modifyNavigationBar(perform: @escaping (UINavigationBar) -> Void) -> some View {
        background(ProxyView {
            sequence(first: $0) { $0.next }
                .lazy
                .compactMap { $0 as? UINavigationController }
                .first { _ in true }
                .map(\.navigationBar)
                .map(perform)
        })
    }
}

struct V: View {
    @ViewBuilder
    var body: some View {
        NavigationStack {
            NavigationLink("Push me") {
                Text("Color changed")
                    .navigationTitle("I have a red bar")
                    .modifyNavigationBar { bar in
                        bar.titleTextAttributes = [.foregroundColor : UIColor.white]
                        bar.backgroundColor = .red
                    }
            }
            .navigationTitle("I have a blue bar")
            .modifyNavigationBar { bar in
                bar.prefersLargeTitles = false
                bar.titleTextAttributes = [.foregroundColor : UIColor.systemYellow]
                bar.backgroundColor = .blue
            }
        }
        .navigationViewStyle(.stack)
    }
}

PlaygroundPage.current.setLiveView(V())

2023.04.22

Switching Between Different Xcodes

John had some questions about Xcode versions. Alex said he used this app to help with the command line xcode-select -s stuff. It is called https://www.xcodes.app

Architecture

Some questions about architecture. There is some overhead to this solution but it puts you in a position to swap out the database implementation later.

https://github.com/joshuajhomann/DatabaseFacade

Git Ignore

Xcode puts stuff in .git/info/exlude
John B. says https://github.com/github/gitignore/blob/main/Swift.gitignore

Converting Objective-C code to Swift

Josh mentions:

https://swiftify.com/converter/code/

Wrapping PNG

Carlyn came up with a way to wrap LibPNG and all of its setjump/longjump error handling.

https://github.com/carlynorama/SwiftLIBPNG/blob/main/META.md

The source will run (eventually) on Linux. She demo'ed it this week.

TimeKeep: Testing with @Dependency

Last week we created a project timer. This week we wrote tests for it.

See https://github.com/rayfix/TimeKeep/tree/main/TimeKeep

import Dependencies
import XCTest

@testable import TimeKeep

final class TimeKeepTests: XCTestCase, @unchecked Sendable {

  var dateValue: Date = .now
  
  func testProjectTimer() {
    var generator = DateGenerator { self.dateValue }
    
    let timer = withDependencies {
      $0.date = generator
    } operation: {
      return ProjectTimer()
    }
    
    XCTAssertFalse(timer.isRunning)
    
    timer.start()
    XCTAssert(timer.isRunning)
        
    timer.stop()
    XCTAssertFalse(timer.isRunning)
    
    dateValue += 1
    
    XCTAssertEqual(timer.elapsed, .zero)
    
    timer.start()
    dateValue += 1
    XCTAssertEqual(timer.elapsed, .seconds(1))
    
    dateValue += 3
    XCTAssertEqual(timer.elapsed, .seconds(4))
    
    // A stopped timer should not record elapsed time.
    timer.stop()
    dateValue += 400
    XCTAssertEqual(timer.elapsed, .seconds(4))
  }
}

Golden Ratio

Josh started with his project. He showed how you can overload operators in Swift to make beautiful syntax for defining golden ratio constants 1 ± √5

2023.04.15

Recording iOS Demo Video

Assistive touch (but it leave some extra chrome that gets recorded)
Use "defaults write com.apple.iphonesimulator ShowSingleTouches 1" (josh)
https://support.screenpal.com/portal/en/kb/articles/show-finger-taps-when-recording-your-screen-on-ios (via Franklin)
https://youtu.be/DAXxgBo-Mr4 (via Franklin)

Evolution

Josh took us through some recent proposals.

is case apple/swift-evolution#2007
Observability https://github.com/apple/swift-evolution/blob/main/proposals/0395-observability.md

TimeKeep

We created a ProjectTimer and introduced the dependency for .now

https://github.com/rayfix/TimeKeep/tree/main/TimeKeep

Mixing SwiftUI and UIKit (Part II)

import Combine
import SwiftUI
import UIKit

import PlaygroundSupport
    
final class VM: ObservableObject {
    @Published var value = 0.0
}
    
final class VC: UIViewController {
    @ObservedObject var viewModel = VM()
    private var subscription: AnyCancellable?
    init() {
        super.init(nibName: nil, bundle: nil)
        let label = UILabel()
        let vm = viewModel
        let button = UIButton(primaryAction: .init(image: .init(systemName: "arrow.counterclockwise"), handler: { _ n vm.value = 0.0 }))
        let slider = ViewBinding(\.value, on: vm) { $value in
            Slider(value: $value).frame(idealWidth: 300)
        }
        let stack = UIStackView(arrangedSubviews: [
            label,
            button,
            UIHostingController(rootView: slider).view
        ])
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.axis = .vertical
        view?.addSubview(stack)
        NSLayoutConstraint.activate([
            view.centerXAnchor.constraint(equalTo: stack.centerXAnchor),
            view.centerYAnchor.constraint(equalTo: stack.centerYAnchor)
        ])
        subscription = viewModel.$value
            .map(String.init(describing:)).map { $0 as String? }
            .assign(to: \.text, on: label)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}
    
PlaygroundPage.current.setLiveView(VC())
    
struct ViewBinding<Target: ObservableObject, Value, Content: View>: View {
    private let keypath: ReferenceWritableKeyPath<Target, Value>
    @ObservedObject private var target: Target
    private let content: (Binding<Value>) -> Content
    
    init(_ keypath: ReferenceWritableKeyPath<Target, Value>,
         on target: Target,
         @ViewBuilder content: @escaping (Binding<Value>) -> Content) {
            self.keypath = keypath
            _target = .init(wrappedValue: target)
            self.content = content
    }
    var body: some View {
        content($target[dynamicMember: keypath])
    }
}

This lets SwiftUI respond to changes from UIKit. The key difference is

let binding = Binding<Double>(get: { vm.value },
                          set: { vm.value = $0 })                          
let slider = Slider(value: binding).frame(idealWidth: 300)

versus:

let slider = ViewBinding(\.value, on: vm) { $value in
  Slider(value: $value).frame(idealWidth: 300)
}

2023.04.08

Discussions

Ed was lamenting the state of HealthKit documentation. In particular, using workouts is not well documented at all.
Activity tracking might be interesting.
Property wrapper projected values $. It can be used to create a binding or get to a publisher depending on where you put it.
Be careful that you don't make your EnvironmentObjects too broad. Any view listening to it will need to rebuild for any change (more precisely when objectWillChange fires).

The PNG Format

Carlyn is exploring the PNG format. She highly recommends the PNG book. Even though it is a little dated, it is extremely well written, informative, and funny.

http://www.libpng.org/pub/png/book/

Her repos:

https://github.com/carlynorama/SwiftLIBPNG

Modern SwiftUI with sample app TimeKeep

Ray is starting a series to talk about modern SwiftUI heavily influenced by https://pointfree.co. Together we are building a small app TimeKeep that lets you track time for multiple projects.

Track the time for multiple projects simultaneously
Multiplatform (iOS, macOS, etc)
Highly testable
Use modern architection

We started this week by building the basic domain and some helper extensions for dealing with dates.

https://github.com/rayfix/TimeKeep/tree/main/TimeKeep

In the process we used point free library Tagged and IdentifiedArrayOf to model the domain as precisely as possible.

Meeting inspired changes

Allen: Change the name of Time to TimeEvent.
Ed: Use Calendar method to tell if two dates are the same day.
Josh: Use static member lookup instead of an enum for the filter predicate.

Next week

We will start putting up some UI.

Mixing SwiftUI and UIKit

Josh gave a great example of how to integrate Swift with UIKit and some of the pitfalls associated with that. The example demonstrates that using a Binding from UIKit to SwiftUI works but binding from SwiftUI to UIKit does not. We will explore how to fix this next week.

import Combine
import SwiftUI
import UIKit
    
import PlaygroundSupport
    
final class VM {
    @Published var value = 0.0
}
    
final class VC: UIViewController {
    private let viewModel = VM()
    private var subscription: AnyCancellable?
    init() {
        super.init(nibName: nil, bundle: nil)
        let label = UILabel()
        let vm = viewModel
        let button = UIButton(primaryAction: .init(image: .init(systemName: "arrow.counterclockwise"), handler: { _ in vm.value = 0.0 }))
        let stack = UIStackView(arrangedSubviews: [
            label,
            button,
            UIHostingController(rootView:
                Slider(value: Binding<Double>(get: { vm.value }, set: { vm.value = $0 })).frame(idealWidth: 300)
           ).view
        ])
        stack.translatesAutoresizingMaskIntoConstraints = false
        stack.axis = .vertical
        view?.addSubview(stack)
        NSLayoutConstraint.activate([
            view.centerXAnchor.constraint(equalTo: stack.centerXAnchor),
            view.centerYAnchor.constraint(equalTo: stack.centerYAnchor)
        ])
        subscription = viewModel.$value.map(String.init(describing:))
          .map { $0 as String? }.assign(to: \.text, on: label)
    }

    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}
    
PlaygroundPage.current.setLiveView(VC())

2023.04.01

Interfacing with C

Carlyn is documenting her explorations into using C libraries from Swift.

Swift One-liners

Franklin brought to our attention that Swift can now be invoked with -e on the command line.

https://blog.eidinger.info/swift-e-runs-code-directly-from-the-command-line

What's New In Swift 5.8

Josh gave us a tour of what is available in Swift 5.8.

https://www.hackingwithswift.com/articles/256/whats-new-in-swift-5-8

Morphology in Foundation

Ray reminded us that you can say, Text("\^[(count) items](inflect: true)") and items will be pluralized properly. It works for other languages too.

https://medium.com/geekculture/automatic-grammar-agreement-b953cbf5d101

Flocking Simulation (Boids)

Josh started a presentation on implementing flocking using Timeline/Canvas in SwiftUI. Some background material:

His implementation used an unsafe to hold the Boid type to prevent reference count traffic. You can learn about that here:

https://www.kodeco.com/7181017-unsafe-swift-using-pointers-and-interacting-with-c

Final Project: TDB

2023.03.25

Swift Ecosystem

Apple is now sponsoring the Swift Package Index.

https://www.swift.org/blog/swift-package-index-developer-spotlight/

Github Changed Host Key

https://github.blog/2023-03-23-we-updated-our-rsa-ssh-host-key/

Using the Camera

Jake working through some issues with purple errors and UIRepresentable.

https://www.kodeco.com/26244793-building-a-camera-app-with-swiftui-and-combine

What's Coming in Swift

A pitch about type-safe predicates:

https://forums.swift.org/t/pitch-swift-predicates/62000

Elide some:

https://forums.swift.org/t/pitch-elide-some-in-swift-6/63737

Parameter Packs

https://github.com/apple/swift-evolution/blob/main/proposals/0393-parameter-packs.md

TikTok Logo Effect: Metal Shaders in CoreImage

The finished project: https://github.com/joshuajhomann/MetalCIFilter

2023.03.18

Swift Packages with C

Carlyn gave us a demo on wrapping a C package with Swift Package Manager:

Also,

https://www.youtube.com/watch?v=6-0UaeJBumA

Debugging Updates

https://www.hackingwithswift.com/quick-start/swiftui/how-to-find-which-data-change-is-causing-a-swiftui-view-to-update

TikTok Logo Effect: Metal Shaders in CoreImage

Josh began creating a sample App that lets you pick an image from your library and apply a color separating effect (think TikTok logo) on the image. This week he showed the main points:

Create a metal file
Add special flag -fcikernel to Other Metal Compiler Flags and Other Metal Linker Flags
Make the function extern "C" so metal can see it.

#include <metal_stdlib>
#include <CoreImage/CoreImage.h>
using namespace metal;

extern "C" {
    auto channelOffset(coreimage::sampler s, float2 redOffset, float2 greenOffset, float2 blueOffset) -> float4 {
        auto index = s.coord();
        return float4(
            s.sample(index - redOffset).r,
            s.sample(index - greenOffset).g,
            s.sample(index - blueOffset).b,
            s.sample(index).a
        );
    }
}

Using the - to subract the offsets is arbitrary. (It could have been + too.)

Learning Shader Graphics:

2023.03.11

What's new in Swift

Swift 5.8 has been released to beta:

https://www.hackingwithswift.com/articles/256/whats-new-in-swift-5-8

Also Swift 5.9 is on the way

https://forums.swift.org/t/swift-5-9-release-process/63557

New actor proposal

Frank's code for his talk about distributed actors: https://github.com/franklefebvre/DistributedActors-FrenchKit

Question from Allen: how to we sync state between SwiftUI and Scenekit

Answer: have a single source of truth:

    final class ViewModel: ObsevableObject {
        @Published var truth
    ...
    }

share with SwiftUI with binding via the projected value of the StateObject:

   childview($viewmodel.binding)

share with SceneKit with a publisher projected fromt he @Published property

   scene(viewmodel.$truth)

Demo: ImageIO

Josh went over the ImageIO library and using it to read files, and image meta data. The full project is below:

https://github.com/joshuajhomann/ImageIOExample

2023.03.04

Conferences

Deep Dish Swift https://deepdishswift.com
Try Swift https://www.tryswift.co/events/2023/nyc/

Escaping Closures

@escaping means they can be stored in a property and used as a callback later.

http://www.goshdarnclosuresyntax.com

Also recommended by Carlyn:

https://www.hackingwithswift.com/quick-start/beginners/how-to-accept-functions-as-parameters

Generative AI for Game Assets

Metal

Josh created an Apple cross-platform app to show how to get Metal going in SwiftUI and created a MetalView. (Watch does not support metal yet.)

Roughly based on:

https://medium.com/@warrenm/thirty-days-of-metal-day-1-devices-e371729d05ca

Also see:

https://developer.apple.com/metal/Metal-Shading-Language-Specification.pdf

You can see some amazing WebGL based demos at:

https://www.shadertoy.com

Project:

https://github.com/joshuajhomann/MetalExample

2023.02.25

WeightedStackView

Josh put together a new type of stack layout that lets each view communicate what weight it wants to the layout system. He wrote the logic for placing views in a functional style and utilized lazy sequences to avoid creation of temporary copies.

See https://developer.apple.com/documentation/swift/lazysequenceprotocol

import PlaygroundSupport
import SwiftUI

struct V: View {
    var body: some View {
        WeightedStackLayout(axis: .vertical, spacing: 0) {
            Color.red.stack(weight: 7)
            Color.green.stack(weight: 5)
            Text("hi").background(Color.yellow)
            Color.blue.stack(weight: 3)
            Color.orange.stack(weight: 2)
            Color.brown.stack(weight: 4)
            Color.cyan.stack(weight: 3)
        }
            .frame(width: 400, height: 400)
    }
}

PlaygroundPage.current.setLiveView(V())

struct WeightedStackLayoutKey: LayoutValueKey {
    static var defaultValue = 1.0
}

extension View {
    func stack(weight: Double) -> some View {
        layoutValue(key: WeightedStackLayoutKey.self, value: weight)
    }
}

extension Layout.Subviews.Element {
    var stackWeight: Double {
        max(self[WeightedStackLayoutKey.self], 1e-6)
    }
}

struct WeightedStackLayout: Layout {
    var axis: Axis = .vertical
    var spacing: CGFloat = 10

    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
        proposal.replacingUnspecifiedDimensions(by: .zero)
    }

    func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
        let totalSpace = CGFloat(subviews.count - 1) * spacing
        let dimension = (axis == .vertical ? bounds.height : bounds.width) - totalSpace
        let pointsPerWeight = dimension / subviews.lazy.map(\.stackWeight).reduce(0, +)
        let weights = subviews.lazy.map(\.stackWeight).accumulated(0, +)
        let points = zip(
            weights.dropLast(),
            weights.dropFirst()
        ).enumerated().lazy.map { offset, element in
            let (startWeight, endWeight) = element
            let spaceBefore = spacing * CGFloat(offset)
            let offset = axis == .vertical ? bounds.origin.y : bounds.origin.x
            return (
                start: startWeight * pointsPerWeight + spaceBefore + offset,
                end: endWeight * pointsPerWeight + spaceBefore + offset
            )
        }
        zip(subviews, points).forEach { view, point in
            let distance = point.end - point.start
            switch axis {
            case .vertical:
                view.place(
                    at: .init(x: bounds.midX, y: point.start + distance / 2),
                    anchor: .center,
                    proposal: .init(width: bounds.width, height: distance)
                )
            case .horizontal:
                view.place(
                    at: .init(x: point.start + distance / 2, y: bounds.midY),
                    anchor: .center,
                    proposal: .init(width: distance, height: bounds.height)
                )
            }
        }
    }

}

struct LazyAccumulatedSequence<Accumulated>: LazySequenceProtocol {
    private let _makeIterator: () -> Iterator
    init<Element>(
        underlying: some Sequence<Element>,
        initial: Accumulated,
        accumulate: @escaping (Accumulated, Element) -> Accumulated
    ) {
        _makeIterator = {
            var iterator = underlying.makeIterator()
            var nextAccumulated: Accumulated? = initial
            return Iterator {
                nextAccumulated.map { accumulated in
                    nextAccumulated = iterator.next().map { next in
                        accumulate(accumulated, next)
                    }
                    return accumulated
                }
            }
        }
    }
    func makeIterator() -> Iterator { _makeIterator() }
    struct Iterator: IteratorProtocol {
        let _next: () -> Accumulated?
        mutating func next() -> Accumulated? { _next() }
    }
}

extension LazySequenceProtocol {
    func accumulated<Accumulated>(
        _ initial: Accumulated,
        _ accumulate: @escaping (Accumulated, Element) -> Accumulated
    ) -> LazyAccumulatedSequence<Accumulated> {
        LazyAccumulatedSequence(underlying: self, initial: initial, accumulate: accumulate)
    }
}

extension Sequence {
    func accumulated<Accumulated>(
        _ initial: Accumulated,
        _ accumulate: (Accumulated, Element) throws -> Accumulated
    ) rethrows -> [Accumulated] {
        var current = initial
        var accumulated = [Accumulated]()
        accumulated.reserveCapacity(underestimatedCount + 1)
        accumulated.append(current)
        for element in self {
            current = try accumulate(current, element)
            accumulated.append(current)
        }
        return accumulated
    }
}

print([1,2,3].accumulated(0, +))

Deep linking in Apps

Josh had an example:

https://github.com/joshuajhomann/PokemonNavigation

Learning AI

General Neural Networks

https://www.youtube.com/watch?v=aircAruvnKk

Running on you own computer

https://github.com/karpathy/nanoGPT

Facebook's Large Language Model

ChatGPT Client for iOS

https://github.com/adamrushy/OpenAISwift.git

2023.02.18

Upcoming Conferences

https://www.tryswift.co/events/2023/nyc/

Edit Kit Pro

From iOSDev weekly, Ed told us about https://digitalbunker.dev/editkit-pro/

URLSessionTaskDelegate

Carlyn is doing some work on the

Models

You can do a lot of work to cleanup models by declaring custom initializers. (You don't have to expose ViewModels but can construct those internally.) You can also use custom Codable to cleanup your code.

Tagged

Ray revisited the Identifier<Tag> type that we looked at in November. The folks over at point free have a library that makes it easy to make unique little types.

https://github.com/pointfreeco/swift-tagged

import Tagged

struct User {
    var id: Tagged<Self, UUID>
}

The point free guys have a whole series on modern SwiftUI development that you can check out on their blog. https://www.pointfree.co/blog

Swift Evolution Proposals

Attached Macros (https://forums.swift.org/t/se-0389-attached-macros/63165)
Expression Macros (https://forums.swift.org/t/se-0382-second-review-expression-macros/63064)
Convenience Async makeStream methods (https://forums.swift.org/t/se-0388-convenience-async-throwing-stream-makestream-methods/63139)

Unicode

Swift Strings are unique in the way that they handle Unicode. Several examples from Josh about how mutation is handled with both String and bridged NSString and NSMutableString. Swift makes a defensive copy for you when assigning.

var a: String = "a"
var b: UnsafeMutablePointer<String> = .init(&a)
a = "b"
print(a,b.pointee)

var c: NSMutableString = "c"
var d: NSString = c
c = "d"
print(c,d)

@propertyWrapper
struct Reference<Value> {
    final class Wrapper<Value> {
        var value: Value
        init(value: Value) {
            self.value = value
        }
    }
    private var wrapper: Wrapper<Value>
    var wrappedValue: Value {
        get { wrapper.value }
        set { wrapper.value = newValue }
    }
    init(wrappedValue: Value) {
        wrapper = .init(value: wrappedValue)
    }
}

var e = Reference(wrappedValue: "e")
var f = e
e.wrappedValue = "f"
print(e.wrappedValue, f.wrappedValue)

["âa", "áb", "àc", "ad", "äe"].lazy.map { string in
    string.contains("a")
}.forEach { print($0) }

["âa", "z", "áb", "àc", "ad", "äe"].sorted { lhs, rhs in
    lhs.lexicographicallyPrecedes(rhs)
}.forEach { print($0) }

["âa", "áb", "àc", "ad", "äe"].lazy.map { string in
    string.localizedStandardContains("a")
}.forEach { print($0) }

["âa", "z", "áb", "àc", "ad", "äe"].sorted { lhs, rhs in
    lhs.localizedCaseInsensitiveCompare(rhs) == .orderedAscending
}.forEach { print($0) }

2023.02.11

Virtual Buddy

A useful tool for creating clean installs. Frank will soon be making a pull request for linux VMs.

Smooth Data

Common methods include moving averages, exponential smoothing, kernel smoothing, and splines.

We discussed a moving average which is probably the simplest. You can do this with a queue.

https://github.com/apple/swift-collections/blob/main/Documentation/Deque.md

Passing Data

Although not discussed on video, this was a side discussion in the chat.

Facebook Engineering

Discussion of the technology Facebook uses (C++, Obj-C++)

https://engineering.fb.com/2023/02/06/ios/facebook-ios-app-architecture/

If you want to do hardcore Swift, Facebook might not be your first choice.

Cross Platform SwiftUI

https://www.scade.io

Although they might only have a small subset of things done.

Swift on the Command Line (Scripting)

Carlyn talked about work she is doing in VS Code and Swift

Link mentioned in chat:

https://rderik.com

A side topic to this was Swift on the Server:

Frank mentioned that the biggest gotcha is differences between implementations on Linux and macOS. Several (Josh and Franklin) noting that this will eventually be solved when Foundation becomes pure Swift:

https://www.swift.org/blog/future-of-foundation/

Wordle Animation!

Josh shows how animation can be brought into the wordle app with a little restructuring. Shows the difference between implicit and explicit animation.

https://github.com/joshuajhomann/Wordle

2023.02.04

Parsing RSS Feeds

RSS is simple XML, so the the old XML Parser API should work.

https://developer.apple.com/documentation/foundation/xmlparser

Frank did some work on this previously. This project might help.

https://github.com/franklefebvre/XMLCoder

Josh implemented a partial SVG reader where he didn't implement all of the callbacks but got the information that he was interested in. See: https://github.com/joshuajhomann/SVGPasteBoard/blob/master/SVGPasteBoard/ContentView.swift

Using Custom Fonts

Ed wants his custom fonts to play nicely with the OS (and respect dynamic type).

Franklin mentioned:

@ScaledMetric(relativeTo: .largeTitle) var dynamicHeader1Size: CGFloat = 24

iOS Podcast GPT

https://www.buzzsprout.com/1414396

Writing Apps with ChatGPT

Emil reports that ChatGPT is helping him to get going with SwiftUI. He has reproduced a major portion of his previous app in SwiftUI in a few days where the original took him months (as he was learning).

Noting that some of the code is old (because ChatGPT was trained before 2021).

The licensing of the code is ambiguous.

Space, the final Frontier

Carlyn mentioned that many of her space friends are excited about this new release:

https://www.penguinrandomhouse.com/books/651844/critical-mass-by-daniel-suarez/

The Nature of Code

Carlyn has been working through these (knows the author) in the last couple of months:

Wordle Clone!

Josh implemented all of the game logic for his wordle clone. He used a reducer that took inputs through a tap gesture recognizer and reduced the state, modifying two properties that drive the UI updates.

https://github.com/joshuajhomann/Wordle

2023.01.28

AsyncImage Fix

Jake had an update to how he was able to fix the animation problem with AsyncImage. Here is the code:

AsyncImage(url: user.profileURL,
           transaction: Transaction(animation: .default)) { phase in
  switch phase {
    case .success(let image):
             image.resizable()
                  .clipShape(Circle())
                  .aspectRatio(contentMode: .fit)
    default:
            ZStack {
              Circle().stroke(.black)
                      .frame(width: 90, height: 90)
              Image(systemName: "person")
                      .font(.title.bold())
                      .scaledToFill()
            }
    }                                  
}.frame(width: 90, height: 90)

Non-uniform shuffling

Carlyn asked about the most Swifty way to enable non-uniform probability picking.

Some suggestions from the group:

Look around in GameKit? (Perhaps look at this: https://www.youtube.com/watch?v=gXnuMk7AVwc)
Create an array with duplicates of the number of elements in the probablilty you want.
Create a special collection that vends the duplicates without actually hosting them in memory.

A related topic: https://en.wikipedia.org/wiki/Rejection_sampling

Speeding up Conformance Checking

We reviewed this blog post about how you can re-order conformance records to get a 20% performance boost.

https://www.emergetools.com/blog/posts/how-order-files-speed-up-protocols

Wurdle (Wordle Clone)

Josh continued his epic presentation on a Wordle clone. Attempted to make it work pretty. Namely, GeometryReader is not greedy and anchors things to the upper-left. You can work around it by adding a ZStack that contains a greedy view like Color.clear or Rectangle().hidden() to the ZStack.

We used the Layout protocol which is a type of view that can explicitly control the layout of a view and its subviews. Josh created a AnchorInParentLayout that lets you align an arbitrary position (UnitPoint) with an arbitrary position of the subview(s). A view modifier makes it easy to use.

2023.01.21

Layout with AsyncImage

Jake was seeing a problem with AsyncImage where the transition animation would be cancelled when the async image loaded. The image would appear at the destination without loading. Josh theorized that the problem was happening because its identity was changing. However, we could not seem to fix the problem by explicitly setting id on the views.

One recommendation is to use a much more capable third party library like Nuke.

https://github.com/kean/Nuke

Dates

Using Core Data to sort by date. Ed says, "CalendarComponents is your friend." Trevor recommended this resource: https://nsdateformatter.com/

Inspiration for UI

Jacey noted that SnapKit is also good (easy) way to layout views.

https://github.com/SnapKit/SnapKit

Sendable

Sendable conformance will be one of the important areas to be aware of as come into Swift 6. You can enable strict concurrency warnings in your build settings. The default is minimal but you can use "targetted" to check your own code.

When you enabled this checking, you will see warnings where an instance is passed across a concurrency domain and is not Sendable. For example:

func findInBackground(quadTree: QuadTree,
                      region: CGRect) async -> Task<[CGPoint], Never> {
  Task.detached {
    quadTree.find(in: region) // WARNING: QuadTree is not Sendable
  }
}

You can mark QuadTree as Sendable to fix this warning. This will, in turn, lead to a warning that Node, the reference type, is not sendable. If you mark Node sendable you get more warnings. This is because the class contains multiple immutable stored properties that could get modified from another concurrency domain. In this case you can mark Node with @unchecked Sendable since you know that all mutation is protected by isKnownUniquelyReferenced and makes a deep copy if it is not unique. (Aka COW.)

Benchmarks

The collection-benchmark project allows you to create benchmarks where the time might be dependent on the size of the input. We created a command-line target and included the benchmark package.

https://github.com/apple/swift-collections-benchmark

We wrote the following benchmarks:

import CollectionsBenchmark
import CoreGraphics.CGBase

struct TestPoints {
  let region: CGRect
  let points: [CGPoint]
  
  init(size: Int) {
    region = CGRect(origin: .zero, size: CGSize(width: size, height: size))
    points = zip((0..<size).shuffled(), (0..<size).shuffled())
      .map { CGPoint(x: $0.0, y: $0.1) }
  }
}


var benchmark = Benchmark(title: "QuadTree Benchmarks")

benchmark.registerInputGenerator(for: TestPoints.self) { size in
  TestPoints(size: size)
}


benchmark.add(title: "QuadTree find",
              input: TestPoints.self) { testPoints in
  
  let tree = QuadTree(region: testPoints.region, points: testPoints.points)
  return { timer in
    testPoints.points.forEach { point in
          let searchRegion = CGRect(origin: point, size: .zero).insetBy(dx: -1, dy: -1)
          blackHole(tree.find(in: searchRegion))
        }
  }
}

benchmark.addSimple(title: "Array<CGPoint> filter",
                    input: TestPoints.self) { testPoints in
  testPoints.points.forEach { point in
    let searchRegion =  CGRect(origin: point, size: .zero).insetBy(dx: -1, dy: -1)
    blackHole(testPoints.points.filter { candidate in
      searchRegion.contains(candidate)
    })
  }
}

benchmark.main()

Then we ran the following commands arguments:

run QuadFindResult.json --cycles 1
render QuadFindResults.json QuadFindResults.png

This produced the following results:

This is a log-log chart and you can see that the growth of the array implementation is linear.

You can see the jump at 4 items which is where the QuadTree logic is kicking in. I found that on my machine, I can boost this constant to 512 to make it always perform better than array.

You can also use a special group file to automatically produce sets of benchmarks and multiple graphs.

Wurdle

Josh continued working on the Wordle game example getting through a lot of the layout issues of the words and keyboard (adding return and backspace).

import SwiftUI

extension Color {
    static let darkGray = Color(#colorLiteral(red: 0.4784313725, green: 0.4823529412, blue: 0.4980392157, alpha: 1))
    static let lightGray = Color(#colorLiteral(red: 0.8274509804, green: 0.8431372549, blue: 0.8549019608, alpha: 1))
    static let darkGreen = Color(#colorLiteral(red: 0.4117647059, green: 0.6705882353, blue: 0.3803921569, alpha: 1))
    static let darkYellow = Color(#colorLiteral(red: 0.7960784314, green: 0.7098039216, blue: 0.3137254902, alpha: 1))
}

struct Row: Hashable, Identifiable {
    var id: Int
    var letters: [Letter]
}

struct Letter: Hashable, Identifiable {
    var id: Int
    var character: Character
    var status: Status
    enum Status: Int, Comparable {
        static func < (lhs: Letter.Status, rhs: Letter.Status) -> Bool { lhs.rawValue < rhs.rawValue }
        case unguessed, wrong, wrongPosition, correct
    }
}

@MainActor
final class GameViewModel: ObservableObject {
    @Published private(set) var words: [Row] = []
    @Published private(set) var keys: [Row] = []
    init() {
        words = ["SWIFT", "CODER", "PLAYA", "     ", "     ", "     "]
            .enumerated()
            .map { word in
                Row(
                    id: word.offset,
                    letters: word.element.enumerated().map { character in
                        Letter(
                            id: word.offset * 10 + character.offset,
                            character: character.element,
                            status: {
                                switch character.element {
                                case " ": return Letter.Status.unguessed
                                case "O", "A": return .correct
                                case "L": return .wrongPosition
                                default: return .wrong
                                }
                            }()
                        )
                    }
                )
            }
        $words
            .map { rows in
                let keys = rows
                    .lazy
                    .flatMap(\.letters)
                    .reduce(into: [Character: Letter.Status]()) { accumulated, next in
                        accumulated[next.character] = accumulated[next.character].map { max($0, next.status) } ?? next.status
                    }
                return ["QWERTYUIOP", "ASDFGHJKL", "ZXCVBNM"]
                    .enumerated()
                    .map { string in
                        Row(
                            id: string.offset,
                            letters: string.element.enumerated().map { character in
                                Letter(
                                    id: string.offset * 100 + character.offset,
                                    character: character.element,
                                    status: keys[character.element] ?? .unguessed
                                )
                            }
                        )
                    }
            }
            .assign(to: &$keys)
    }
}

struct ContentView: View {
    @StateObject var viewModel = GameViewModel()
    var body: some View {
        GeometryReader { reader in
            VStack(spacing: 36) {
                Grid(alignment: .topLeading, horizontalSpacing: 12, verticalSpacing: 12) {
                    ForEach(viewModel.words) { row in
                        GridRow {
                            ForEach(row.letters) { letter in
                                LetterView(style: .word(letter))
                            }
                        }
                    }
                }
                .frame(maxWidth: 600)
                VStack (spacing: 12) {
                    ForEach(viewModel.keys) { row in
                        HStack(spacing: 8) {
                            if viewModel.keys.last == row {
                                LetterView(style: .keyImage("return"))

                                keys(for: row)
                                LetterView(style: .keyImage("delete.backward"))

                            } else {
                                keys(for: row)
                            }
                        }
                    }
                }
            }
            .padding()
        }
    }

    private func keys(for row: Row) -> some View {
        ForEach(row.letters) { letter in
            LetterView(style: .key(letter))
        }
    }
}

struct LetterView: View {
    var style: Style
    enum Style {
        case key(Letter), word(Letter), keyImage(String)
    }
    private let fontSize: CGFloat
    private let aspectRatio: CGFloat
    private let textColor: Color
    private let backgroundColor: Color
    private let outlineColor: Color

    init(style: Style) {
        self.style = style
        switch style {
        case .keyImage:
            aspectRatio = 0.66 * 1.5
            fontSize = 48
            textColor = .black
            backgroundColor = .lightGray
            outlineColor = .clear
        case let .key(letter):
            aspectRatio = 0.66
            fontSize = 48
            (textColor, backgroundColor, outlineColor) = colors(for: letter, isKey: true)
        case let .word(letter):
            aspectRatio = 1
            fontSize = 100
            (textColor, backgroundColor, outlineColor) = colors(for: letter, isKey: false)
        }
        func colors(for letter: Letter, isKey: Bool) -> (Color, Color, Color) {
            switch (letter.status, isKey) {
            case (.unguessed, true): return (.black, .lightGray, .clear)
            case (.unguessed, false): return (.black, .white, .black)
            case (.correct, _): return (.white, .darkGreen, .clear)
            case (.wrongPosition, _): return (.white, .darkYellow, .clear)
            case (.wrong, _): return (.white, .darkGray, .clear)
            }
        }
    }

    var body: some View {
        GeometryReader { proxy in
            RoundedRectangle(cornerRadius: 8)
                .strokeBorder(outlineColor, lineWidth: 4)
                .background(RoundedRectangle(cornerRadius: 8).fill(backgroundColor))
                .overlay {
                    switch style {
                    case let .keyImage(name):
                        Image(systemName: name)
                    case let .key(letter), let .word(letter):
                        Text(String(describing: letter.character))
                    }
                }
                .foregroundColor(textColor)
                .font(.system(size: fontSize, weight: .bold))
        }
        .aspectRatio(aspectRatio, contentMode: .fit)
    }
}

2023.01.14

PointFree Dependency Injection

A new library for dependency injection was announced this week by the folks at pointfree.co. Josh gave us a quick tour of the library and an additions library:

https://github.com/pointfreeco/swift-dependencies

Peter posted this example of using the additions library:

https://twitter.com/tgrapperon/status/1612698675356250114

Ed Launches Testflight

Ed launched a private testfligt build for his new app. During the coarse of the meeting was able to find and fix an out of bounds crasher when there is no data. The power of testing in action.

Learning Swift

Some of the tried and true:

Async Result

You can create an async init for result types to get clean monadic chaining instead of nested do {} catch {} blocks. Daniel and Josh showed us how!

CoreData

Core Data is a deep subject. A good place to start:

https://developer.apple.com/documentation/coredata/setting_up_a_core_data_stack

Noise Generation

GameKit although old and written in ObjectiveC, has API for creating "natural" noise often used for procedural terrain generation in games.

https://developer.apple.com/documentation/gameplaykit/gknoisemap

Wurdle

As part of another epic, multipart demo, Josh is implementing a version of the popular game in SwiftUI. Today he created the basic model for Rows and Letters and Keys as well as the Status for each.

2023.01.07

Using contraMap Example

You can write a contramap function on CurrentValueSubject<Int> to make functions that can send other types into the current value.

import Foundation
import Combine

extension CurrentValueSubject {
    func contraMap<Value>(transform: @escaping (Value) -> Output) -> (Value) -> Void {
      { [weak self] input in
          self?.send(transform(input))
      }
    }
}

let subject = CurrentValueSubject<Int, Never>(0)
let sendBool = subject.contraMap { (bool: Bool) in bool ? 1 : 0 }
sendBool(true)
print(subject.value)

Learning SwiftUI

Core Data Debugging

Suggestions for Dan's app that has a crashing problem:

Log non-fatal errors
Think about all of the validations done by the Core Data model
It reliably crashes on start
Take note of the OS / devices it is happening on in the crash logs
Debugging concurrency issues with -com.apple.CoreData.ConcurrencyDebug 1

Returning Swift Conferences

https://deepdishswift.com
https://www.swiftconf.to
https://tryswift.jp (meetup style on 1/21)

Swift Charts Performance

Ed wrote his own charts with GeometryReader instead of SwiftUI Charts because of performance problems on rotation and scrolling.

Photo Picker iOS16

Jake reports it is awesome.
Requires user iteraction so no permission is required.
https://developer.apple.com/documentation/photokit/photospicker

New Swift Proposals

https://www.swift.org/swift-evolution/

SE-0383 Deprecate @UIApplicationMain and @NSApplicationMain
SE-0384 Importing Forward Declared Objective-C Interfaces and Protocols
SE-0382 Expression Macros

Compression

The new multicore APFS aware Apple Archive framework: https://developer.apple.com/documentation/applearchive

Swift Collections

Josh took us on a guided tour of the Swift Collections package.

https://github.com/apple/swift-collections

Exploration of CHAMP:

Aside: A Benchmarking Tool

https://github.com/apple/swift-collections-benchmark

JSON with decode indirect enum

You can represent JSON with swift with this:

enum JSON {
	indirect case array([JSON])
	indirect case dictionary([String: JSON])
	case boolean(Bool)
	case number(Double)
	case string(String)
	case null
}

You can implement Decodable using a single value container. Naively it is a bunch of nested do {} catch {} blocks but it can be done quite succinctly by using a Result type and flatMapError to implement successive retries.

enum JSON {
    indirect case array([JSON])
    indirect case dictionary([String: JSON])
    case boolean(Bool)
    case number(Double)
    case string(String)
    case null
}

extension JSON: Decodable {
    init(from decoder: Decoder) throws {
        self = try Result { try decoder.singleValueContainer() }
            .flatMap { container in
                container.decodeNil()
                    ? .success(JSON.null)
                    : Result { JSON.boolean(try container.decode(Bool.self)) }
                        .flatMapError { _ in Result { JSON.number(try container.decode(Double.self)) } }
                        .flatMapError { _ in Result { JSON.string(try container.decode(String.self)) } }
                        .flatMapError { _ in Result { JSON.array(try container.decode([JSON].self)) } }
                        .flatMapError { _ in Result { JSON.dictionary(try container.decode([String: JSON].self)) } }
            }.get()
    }
}

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