Added introspect for scroll view in TabBarView with PageTabViewStyle

[philprime]

I created an extension to introspect the horizontal scroll view in a TabBarView with tabViewStyle(PageTabViewStyle().

This tab view style is Apple's solution for pagination like UIPageViewController. Interesting enough, it actually uses a UICollectionView with an embedded UIScrollView.

I use this extension to disable horizontal scrolling (similar to scrollView.isScrollEnabled = false) so only programmatic navigation is possible. When horizontal scrolling is disabled, the collection view still bounces vertically, so both views are passed to the customize closure.

Example:

import SwiftUI
import Introspect

@main
struct DemoApp: App {

    @State private var selection = 1

    var body: some Scene {
        WindowGroup {
            TabView(selection: $selection) {
                Button("Go To Page 2", action: {
                    withAnimation {
                        selection = 2
                    }
                })
                .tag(1)
                Button("Go To Page 1", action: {
                    withAnimation {
                        selection = 1
                    }
                })
                .tag(2)
            }
            .tabViewStyle(PageTabViewStyle())
            .introspectPagedTabView { collectionView, scrollView in
                collectionView.isScrollEnabled = false
                scrollView.isScrollEnabled = false
            }
        }
    }
}

[bratxdy]

Any chance we can get this into master and released? We were using .introspectScrollView previously on a TabView with PageTabViewStyle to get the scroll view to turn off vertical bouncing and it broke when updating to 0.1.1, likely by 6ddd059

[dannyhertz]

+1 can we get this merged?

[joshuakcockrell]

This is working great for me! Setting the collectionView or scrollView delegate methods breaks the TabBar though.. SwiftUI must be doing some magic behind the scenes with the delegates.

[guillecom]

Tested this and it works in ios 15.4

[SplittyDev]

@philprime thanks a lot for the PR and sorry for the late reply!
I'd love to merge this, could you add tests to make sure this works as intended on all platforms?

[philprime]

@SplittyDev I think I can do that, but I need assistance on how to create Introspect tests cases -> how do you verify it works?

[SplittyDev]

@SplittyDev I think I can do that, but I need assistance on how to create Introspect tests cases -> how do you verify it works?

@philprime In the IntrospectTests directory we have AppKitTests.swift and UIKitTests.swift. If an introspection works for both, we write two separate tests for AppKit and UIKit, otherwise we just write one for the correct platform.

We create a view for the test (e.g. TabBarTestView / PageTabViewStyleTestView), where the target component is introspected and a function (called a spy) is called from within the introspection.

We then write the test itself, which renders the test view and passes an XCTestExpectation to the component as the spy function. Then we present the component using a small helper utility and verify that the spy was called.

One more important thing is that the components / introspections are properly tagged with @available annotations, here is an example from the ColorWellTestView:

@available(iOS 14.0, tvOS 13.0, macOS 11.0, *)
@available(tvOS, unavailable)
private struct ColorWellTestView: View { ... }

Platform availability information can usually be taken directly from the docs:
Apple Docs: https://developer.apple.com/documentation/swiftui/pagetabviewstyle

[philprime]

@SplittyDev I added a test case as you described it. Let me know if more changes are required.

(Sorry for the formatting commits/notifications, for some reason it kept being wrong 😂)

[SplittyDev]

@philprime good stuff, thanks a lot! The formatting commits aren't a problem, we'll squash-merge anyway :)

[ichikmarev]

@SplittyDev Hi. This awesome PR was merged but seemed lost since it is not in 0.1.4.

[philprime]

@ichikmarev actually the PR hasn't been released yet.

My commit is in the main branch with date April 17th, 2022, but the release 0.1.4 was published on January 26, 2022