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Sample Swift Project

  • iOS Example

If you are getting started with Swift and iOS development you should be able to use this guide, although this guide is recommended for those familiar with iOS development and the Swift language. This is a simplified guide to integrate the XYO Core Swift SDK.

For the source code refer to this link

Table of Contents

App Structure

  • Swift with Xcode and Cocoapods

Click here for an introduction to integrate a new Xcode project with CocoaPods

Versions used in this sample

  • XCode 10.3
  • Swift 5.0.1

It is important to set up this project with CocoaPods so you can use dependencies to build the app

Using Xcode

Virtual Device Emulator

When creating the configuration for the emulator, we recommend using a mid-range device definition for a wider range of coverage for iOS devices. (Such as a iPhone XR) feel free to use whatever example iOS device you would like.

This sample app is best for mobile devices

This Sample App Example is best for mobile devices since bound witnessing is optimal on mobile. Integration into your application should be based on a mobile app architecture.

Create the Project

Install Pod and Start Up Project

For the podfile, we will go ahead and use the latest sdk-core-swift

target 'MyApp' do 
  pod 'sdk-core-swift', '3.0'
end

Then run a pod install from your terminal

Once the pod installation is complete we open the workspace

open MyApp.xcworkspace

You should now see your Xcode workspace

All of our work will be in the ViewController.swift file

Start with Creating a Bound Witness

For this integration guide we will do our work in the view controller.

Go here for the source code of the complete project

We want to start by importing our core_swift and objectmodel SDKs

import sdk_core_swift
import sdk_objectmodel_swift

We should see the following in our ViewController.swift

class ViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
  }
}

Set up the values needed for origin chain

In order for us to do a bound witness we need some objects and interfaces

class ViewController: UIViewController {
  private let hasher = XyoSha256()
  private let store = XyoInMemoryStorage()
  private lazy var state = XyoStorageOriginStateRepository(storage: store)
  private lazy var blocks = XyoStorageProviderOriginBlockRepository(storageProvider: store, hasher: hasher)
  private lazy var conf = XyoRepositoryConfiguration(originState: state, originBlock: blocks)
  private lazy var node = XyoOriginChainCreator(hasher: hasher, repositoryConfiguration: conf)
}

Set up the listener

Let us add an extension to our ViewController to get the node listener that we'll need to display the hash representation of our bound witness

extension ViewController : XyoNodeListener {
  // the library will bring some of these functions in, but we won't need most of them
  func onBoundWitnessStart() {}
  func onBoundWitnessEndFailure() {}
  func onBoundWitnessDiscovered(boundWitness: XyoBoundWitness) {} 

// this is where we bring in and display our bound witness
  func onBoundWitnessEndSuccess(boundWitness: XyoBoundWitness) {
    let hash = (try? boundWitness.getHash(hasher: hasher))?.getBuffer().toByteArray().toHexString()

  }
}

Project Design

Before we can actually display the hash we need to set up the UI

Set up the UI

Let's create the bound witness text to display, we will use the UILabel view class

private lazy var doBoundWitness: UILabel = {
  let text = UILabel()

  text.textColor = UIColor.black
  text.font = UIFont.systemFont(ofSize: 20, weight: .black)
  text.numberOfLines = 0

  return text
}()

We can now set the text in our listener which will be the hash

func onBoundWitnessEndSuccess(boundWitness: XyoBoundWitness) {
  let hash = (try? boundWitness.getHash(hasher: hasher))?.getBuffer().toByteArray().toHexString()

  doBoundWitness.text = hash
}

In order for us to call the listener and get our hash, we need to create a button, we will use the UIButton class

private lazy var doBoundWitnessButton: UIButton = {
  let button = UIButton(type: UIButton.ButtonType.roundedRect)

  button.setTitle("Create Origin", for: UIControl.State.normal)

  return button
}()

Add logic to the button

private func layoutButton () {
    view.addSubview(doBoundWitnessButton)
    doBoundWitnessButton.translatesAutoresizingMaskIntoConstraints = false
    doBoundWitnessButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    doBoundWitnessButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

    let click = UITapGestureRecognizer(target: self, action: #selector(onButtonClick(_:)))
    doBoundWitnessButton.addGestureRecognizer(click)
}

Add interactivity to the button

@objc func onButtonClick (_ sender: UITapGestureRecognizer) {
  // error check without crashing
    try? node.selfSignOriginChain()
}

Now we have a button to activate the listener and display a bound witness hash on our primary view.

Set up the rest of the view

Before setting up the entire layout, let's create a title

private lazy var appTitle: UILabel = {
  let text = UILabel()

  text.textColor = UIColor.purple

  text.font = UIFont.systemFont(ofSize: 20, weight: .black)

  text.numberOfLines = 0

  return text
}()

We should create a layout where we can have our viewDidLoad() function call for what text and interactivity we want on this simple app

private func layout() {
  // bring in a title 
  appTitle.text = "Sample XYO App"

  view.addSubView(appTitle)
  view.addSubView(doBoundWitness)

  appTitle.translatesAutoresizingMaskIntoConstraints = false
  appTitle.topAnchor.constraint(equalTo: view.topAnchor, constant: 150).isActive = true
  appTitle.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

  doBoundWitness.translatesAutoresizingMaskIntoConstraints = false
  doBoundWitness.bottomAnchor.constraint(equalTo: doBoundWitnessButton.topAnchor, constant: -80).isActive = true

}

Now we can include the layouts in our primary view

override func viewDidLoad() {
  super.viewDidLoad()
  node.addListener(key: "main", listener: self)
  layout()
  layoutButton()
}

Once you update the viewDidLoad(), your code should currently look like this

import UIKit
import sdk_core_swift
import sdk_objectmodel_swift

class ViewController: UIViewController {
    private let locationManager = CLLocationManager()
    private let hasher = XyoSha256()
    private let store = XyoInMemoryStorage()
    private lazy var state = XyoStorageOriginStateRepository(storage: store)
    private lazy var blocks = XyoStorageProviderOriginBlockRepository(storageProvider: store, hasher: hasher)
    private lazy var conf = XyoRepositoryConfiguration(originState: state, originBlock: blocks)
    private lazy var node = XyoOriginChainCreator(hasher: hasher, repositoryConfiguration: conf)

    private lazy var doBoundWitnessButton: UIButton = {
        let button = UIButton(type: UIButton.ButtonType.roundedRect)
        
        button.setTitle("Create Origin", for: UIControl.State.normal)
        
        return button
    }()

    private lazy var doBoundWitness: UILabel = {
        let text = UILabel()
        
        text.textColor = UIColor.black
        
        text.font = UIFont.systemFont(ofSize: 20, weight: .black)
        
        text.numberOfLines = 0
        
        return text
    }()

    private lazy var appTitle: UILabel = {
        let text = UILabel()
        
        text.textColor = UIColor.purple
        
        text.font = UIFont.systemFont(ofSize: 20, weight: .black)
        
        text.numberOfLines = 0
        
        return text
        
    }()

    override func viewDidLoad() {
        super.viewDidLoad() 
        node.addListener(key: "main", listener: self)
        layout()
        layoutButton()
    }

    private func layout () {
        appTitle.text = "Sample XYO App"
        
        view.addSubview(appTitle)
        view.addSubview(doBoundWitness)
        
        appTitle.translatesAutoresizingMaskIntoConstraints = false
        appTitle.topAnchor.constraint(equalTo: view.topAnchor, constant: 150).isActive = true
        appTitle.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        
        doBoundWitness.translatesAutoresizingMaskIntoConstraints = false
                
        doBoundWitness.bottomAnchor.constraint(equalTo: doBoundWitnessButton.topAnchor, constant: -80).isActive = true
        doBoundWitness.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        doBoundWitness.widthAnchor.constraint(equalTo: view.widthAnchor, constant: -80).isActive = true
    }

    private func layoutButton () {
        view.addSubview(doBoundWitnessButton)
        doBoundWitnessButton.translatesAutoresizingMaskIntoConstraints = false
        doBoundWitnessButton.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        doBoundWitnessButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        let click = UITapGestureRecognizer(target: self, action: #selector(onButtonClick(_:)))
        doBoundWitnessButton.addGestureRecognizer(click)
    }

    @objc func onButtonClick (_ sender: UITapGestureRecognizer) {

        try? node.selfSignOriginChain()
    }

}

  extension ViewController : XyoNodeListener {
      // not needed
      func onBoundWitnessStart() {}
      func onBoundWitnessEndFailure() {}
      func onBoundWitnessDiscovered(boundWitness: XyoBoundWitness) {}

      func onBoundWitnessEndSuccess(boundWitness: XyoBoundWitness) {
          let hash = (try? boundWitness.getHash(hasher: hasher))?.getBuffer().toByteArray().toHexString()
          doBoundWitness.text = hash
      }

  }
}

Run the project

Go ahead and save the project and run the build by clicking on the play button on the top left hand side of the Xcode IDE

You should now see the Create Origin button and when you tap it you should see a response on the screen with the hash value of the newly created bound witness chain. You can tap again for another bound witness chain.

Add Location

Let's keep going. We want to add a heuristic and see what heuristic we are adding. We'll add a GPS location to our bound witness chain.

Let's start by briging in the Swift location manager in the first line of the ViewController class.

private let locationManager = CLLocationManager()

We should create a new text field to be ready for the location information that we want the user to see. That way the user knows what the heuristic we are adding to the origin chain.

    private lazy var doLocation: UILabel = {
        let text = UILabel()
        
        text.textColor = UIColor.red
        
        text.font = UIFont.systemFont(ofSize: 13, weight: .black)
        
        return text
    }()

We should add permissions.

In viewDidLoad()

  locationManager.requestWhenInUseAuthorization()

Now we can add an extension to add the location heuristic. You can look at the primary readme guide for an example of the getHeuristic method.

Now let's create a new extension for the getter

extension ViewController : XyoHeuristicGetter {
    func getHeuristic() -> XyoObjectStructure? {
        guard let lat: Double = locationManager.location?.coordinate.latitude else {
            return nil
        }

        guard let lng: Double = locationManager.location?.coordinate.longitude else {
            return nil
        }
        
        doLocation.text = "\(lat), \(lng)"
        
        let encodedLat = XyoObjectStructure.newInstance(schema: XyoSchemas.LAT, bytes: XyoBuffer(data: anyToBytes(lat)))
        let encodedLng = XyoObjectStructure.newInstance(schema: XyoSchemas.LNG, bytes: XyoBuffer(data: anyToBytes(lng)))
        return XyoIterableStructure.createUntypedIterableObject(schema: XyoSchemas.GPS, values: [encodedLat, encodedLng])
        
    }

    func anyToBytes<T>(_ value: T) -> [UInt8] {
        var value = value
        return withUnsafeBytes(of: &value) { Array($0) }.reversed()
    }

}

Once we get the user's permission, we get the last known location if there is one, then we encode the location coordinates before we create a new XyoObjectStructure for the heuristic to be compatible with our origin chain object.

We also add a doLocation.text to print out the non-encoded location coordinates so that the user can see a human readable version of the location that is added to the origin chain.

Once we have the resolver set, we can plug it into the addHeuristic method to the view loader

viewDidLoad()

override fun onCreate(savedInstanceState: Bundle?) {
  ...
  node.addHeuristic(key: "gps", getter: self)
}

We then should enable updating location

locationManager.startUpdatingLocation()

The viewDidLoad() should look like this when we are done

    override func viewDidLoad() {
        super.viewDidLoad()
        
        locationManager.requestWhenInUseAuthorization()
        node.addListener(key: "main", listener: self)
        node.addHeuristic(key: "gps", getter: self)
        locationManager.startUpdatingLocation()
        layoutButton()
        layout()
    }

Now we can add our doLocation view to our Layout

    private func layout () {
        ...

        view.addSubview(doLocation)
        
        doLocation.translatesAutoresizingMaskIntoConstraints = false
        
        doLocation.bottomAnchor.constraint(equalTo: doBoundWitnessButton.topAnchor, constant: 100).isActive = true
        doLocation.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

    }

Now rebuild and run the app.

When you tap or click (in a simulator) the create origin button, you should see the GPS coordinate appear right before the hash.

Conclusion

You have now created an origin chain and added the gps heuristic to the origin chain.

Made with 🔥and ❄️ by XY - The Persistent Company