Adds viewDidAppear callback to SwiftUI

OnDidAppearSwiftUI

struct ViewControllerLifecycleHandler: UIViewControllerRepresentable {
    func makeCoordinator() -> ViewControllerLifecycleHandler.Coordinator {
        Coordinator(onDidAppear: onDidAppear)
    }

    let onDidAppear: () -> Void
    
    func makeUIViewController(context: UIViewControllerRepresentableContext<ViewControllerLifecycleHandler>) -> UIViewController {
        context.coordinator
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<ViewControllerLifecycleHandler>) {
    }

    typealias UIViewControllerType = UIViewController

    class Coordinator: UIViewController {
        let onDidAppear: (() -> Void)?

        init(onDidAppear: (() -> Void)?) {
            self.onDidAppear = onDidAppear

            super.init(nibName: nil, bundle: nil)
        }

        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        override func viewDidAppear(_ animated: Bool) {
            super.viewDidAppear(animated)
           (onDidAppear ?? {})()
        }
    }
}

struct DidAppearModifier: ViewModifier {
    let onDidAppearCallback: (() -> Void)?

    func body(content: Content) -> some View {
        content
            .background(ViewControllerLifecycleHandler(onDidAppear: onDidAppearCallback ?? {}))
    }
}

extension View {
    func onDidAppear(_ perform: @escaping () -> Void) -> some View {
        self.modifier(DidAppearModifier(onDidAppearCallback: perform))
    }
}

Yeah, sure... @alongotv

var body: some View {
        TabView {
            ForEach(0..<5) { item in 
                FruitCardView()
            } //: FOREACH
        } //: TABVIEW
        .tabViewStyle(PageTabViewStyle())
        .padding(.vertical, 20)
    }

// FRUITCARDVIEW
var body: some View {
        ZStack {
            VStack(spacing: 20) {
                // IMAGE
                ...
                // TITLE
                ...
                // HEADLINE
                ...
                // START
                ...
            } //: VSTACK
        } //: ZSTACK
        .onDidAppear {
            withAnimation(.easeOut(duration: 0.5)) {
                print("IS ANIMATING: \(isAnimating)")
                isAnimating = true
            }
        }
        
    }

Where u get this log:

IS ANIMATING: false
IS ANIMATING: false
IS ANIMATING: true
IS ANIMATING: false

As you can see, the 3 view in the TabView is created before it even appears...

@Alexminator99 It looks like something might be broken in TabView once again - I can't receive viewDidAppear callback in the UIViewControllerRepresentable if applied to View inside the TabView (iOS 16.1.1 physical device). Although, viewWillAppear works just fine. Unfortunately, I was unable to find a workaround, other than using that modifier outside the TabView or putting the TabView's child into a ".sheet{}". Either way, it's a pity that this gist wasn't helpful for you. Sorry!

@Alexminator99 It looks like something might be broken in TabView once again - I can't receive viewDidAppear callback in the UIViewControllerRepresentable if applied to View inside the TabView (iOS 16.1.1 physical device). Although, viewWillAppear works just fine. Unfortunately, I was unable to find a workaround, other than using that modifier outside the TabView or putting the TabView's child into a ".sheet{}". Either way, it's a pity that this gist wasn't helpful for you. Sorry!

I already reported the issue. Thks anyway, the gist is really interesting ;)

Just stumbled upon this discussion and I think that this might be related: feedback-assistant/reports#411

Had an issue where it wasn't recognizing the ViewModifier as valid, changed some stuff around and now it works:

struct ViewControllerLifecycleHandler: UIViewControllerRepresentable {
    func makeCoordinator() -> ViewControllerLifecycleHandler.Coordinator {
        Coordinator(onDidAppear: onDidAppear)
    }

    let onDidAppear: () -> Void
    
    func makeUIViewController(context: UIViewControllerRepresentableContext<ViewControllerLifecycleHandler>) -> UIViewController {
        context.coordinator
    }

    func updateUIViewController(_ uiViewController: UIViewController, context: UIViewControllerRepresentableContext<ViewControllerLifecycleHandler>) {
    }

    typealias UIViewControllerType = UIViewController

    class Coordinator: UIViewController {
        let onDidAppear: (() -> Void)?

        init(onDidAppear: (() -> Void)?) {
            self.onDidAppear = onDidAppear

            super.init(nibName: nil, bundle: nil)
        }

        required init?(coder: NSCoder) {
            fatalError("init(coder:) has not been implemented")
        }
        
        override func viewDidAppear(_ animated: Bool) {
            super.viewDidAppear(animated)
           (onDidAppear ?? {})()
        }
    }
}

extension View {
    func onDidAppear(_ perform: @escaping () -> Void) -> some View {
        return background(ViewControllerLifecycleHandler(onDidAppear: perform))
    }
}

Hope this helps anyone else trapped on older versions of iOS!