UIKit的 viewDidAppear() 和 viewDidDisappear() 等价于SwiftUI的方法onAppear() 和 onDisappear()

1.示例

struct ContentView: View {
    var body: some View {
        NavigationView {
            VStack {
                NavigationLink(destination: DetailView()) {
                    Text("Hello World")
                }
            }
            .onAppear {
                print("ContentView appeared!")
            }
            .onDisappear {
                print("ContentView disappeared!")
            }
        }
    }
}

struct DetailView: View {
    var body: some View {
        VStack {
            Text("Second View")
        }
        .onAppear {
            print("DetailView appeared!")
        }
        .onDisappear {
            print("DetailView disappeared!")
        }
    }
}

原文:https://www.hackingwithswift.com/quick-start/swiftui/how-to-respond-to-view-lifecycle-events-onappear-and-ondisappear