animate(changes:completion:)

Declaration

@backDeployed(before: macOS 15.4)
@MainActor @preconcurrency func animate(changes: () -> Void, completion: (() -> Void)? = nil)

Parameters

• changes:

  A closure that changes animatable properties.

• completion:

  A closure to execute after the animation completes.

Discussion

This combines doc://com.apple.documentation/documentation/appkit/nsanimationcontext/4433144-animate with the current transaction’s animation. When you start a SwiftUI animation using withAnimation(_:_:) and have a mutated SwiftUI state that causes the representable object to update, use this method to animate changes in the representable object using the same Animation timing.

struct ContentView: View {
    @State private var isCollapsed = false
    var body: some View {
        ZStack {
            MyDetailView(isCollapsed: isCollapsed)
            MyRepresentable(isCollapsed: $isCollapsed)
            Button("Collapse Content") {
                withAnimation(.bouncy) {
                    isCollapsed = true
                }
            }
        }
    }
}

struct MyRepresentable: NSViewControllerRepresentable {
    @Binding var isCollapsed: Bool

    func updateNSViewController(_ nsViewController: NSViewControllerType, context: Context) {
        if isCollapsed && !nsViewController.view.isCollapsed {
            context.animate {
                nsViewController.view.collapseSubview()
                nsViewController.view.layoutSubtreeIfNeeded()
            }
        }
    }
}