1import SwiftUI
2
3/// Defers the rendering of a view for the given period.
4///
5/// For example:
6///
7/// ```swift
8/// Text("Hello, world!")
9///     .deferredRendering(for: .seconds(5))
10/// ```
11///
12/// will not display the text "Hello, world!" until five seconds after the
13/// view is initially rendered.  If the view is destroyed within the delay,
14/// it never renders.
15///
16/// This is based on code xwritten by Yonat and Charlton Provatas on
17/// Stack Overflow, see https://stackoverflow.com/a/74765430/1558022
18///
19private struct DeferredViewModifier: ViewModifier {
20    let delay: DispatchTimeInterval
21
22    func body(content: Content) -> some View {
23        _content(content)
24            .onAppear {
25               DispatchQueue.main.asyncAfter(deadline: .now() + delay) {
26                   self.shouldRender = true
27               }
28            }
29    }
30
31    @ViewBuilder
32    private func _content(_ content: Content) -> some View {
33        if shouldRender {
34            content
35        } else {
36            content.hidden()
37        }
38    }
39
40    @State private var shouldRender = false
41}
42
43extension View {
44    func deferredRendering(for delay: DispatchTimeInterval) -> some View {
45        modifier(DeferredViewModifier(delay: delay))
46    }
47}
48
49struct DeferredRendering_Previews: PreviewProvider {
50    static var previews: some View {
51        VStack {
52            Text("This text renders immediately")
53            Text("This text appears after a delay")
54                .deferredRendering(for: .seconds(1))
55        }
56    }
57}