ios – Different behavior when initializing object within init() vs onAppear – Confused

If have tinkered with Swift AVAudioPlayer.

Currently I’m confused because when I initialize the object within onAppear, then everything works fine.

When I use init() for initialization, then the object is nil afterwards.

I used the debugger: It’s perfectly clear, that the code within init, has been executed before the object becomes used. Nevertheless it’s nil, respectively “” afterwards.

What goes wrong here?

Can someone explain the described findings?

import AVFAudio

struct ContentView: View {
    @State var player: AVAudioPlayer? = nil
    @State var isPlaying = false
    
    let url = Bundle.main.url(forResource: "demo01", withExtension: "m4a")
    // Results in 
    init() {
//      if let url {
//          do {
//              player = try AVAudioPlayer(contentsOf: url)
//          } catch {
//              print(error.localizedDescription)
//          }
//      }
    }
    
    var body: some View {
        VStack(spacing: 25) {
            Button {
                if let player {
                    if (isPlaying == true) {
                        player.pause()
                        isPlaying = false
                    } else {
                        player.prepareToPlay()
                        player.play()
                        isPlaying = true
                    }
                }
            } label: {
                Label(isPlaying ? "Pause" : "Play",
                      systemImage: isPlaying ? "stop.circle" : "play.circle")
            }
        }
        .onAppear() {
            if let url {
                do {
                    player = try AVAudioPlayer(contentsOf: url) // 
                } catch {
                    print(error.localizedDescription)
                }
            }
        }
        .padding()
    }
}