ios - 当我使用属性更新 View 时，ObservedObject将重置。因此会导致数据丢失

我有一个问题，在更新视图时，ViewModel将重新初始化。

我有2个视图，SongListView和PlayerView共享一个Player对象。当玩家的游戏状态更改为(isPlaying == true)时，viewModel中的SongListView重置并变为空数组。因此，我视图上的列表变为空。



SongListView:

struct SongListView: View {

    @ObservedObject var model: SongListViewModel = SongListViewModel() // This resets when player.isPlaying is set to true

    @ObservedObject var player: Player

    var body: some View {

        List(model.songs, id: \.id) { song in
            Button(action: {
                self.player.play(link: song.link)
            }) {
                TitleRowView(title: song)
            }
        }
        .onAppear {
            self.model.get()
        }
        .navigationBarTitle(Text("Songs"), displayMode: .inline)
    }
}

SongListViewModel:

class SongListViewModel: ObservableObject {

    @Published var songs: [Song] = [Song(id: 2, name: "ish", link: "ishm")] // When I tap the row, the songs var is re-initialized

    func get() {

        guard let url = URL(string: "apiPath") else { return }

        URLSession(configuration: URLSessionConfiguration.default).dataTask(with: url) {data, response, error
               // Some more code
               self.songs = data
        }.resume()
    }
}

PlayerView:

struct PlayerView: View {

    @ObservedObject var player: Player

    var body: some View {
        HStack {
            Button(action: {
                if self.player.isPlaying {
                    self.player.pause()
                } else {
                    self.player.play()
                }
            }) {
                // This change causes the viewModel to reset to empty array
                if self.player.isPlaying {
                    Image(systemName: "pause.fill")
                        .resizable()
                } else {
                    Image(systemName: "play.fill")
                        .resizable()
                }
            }
        }
    }
}

玩家:

class Player : ObservableObject
{

    @Published var isPlaying: Bool = false

    private var player: AVPlayer?

    // This method is called when the user taps on a row in List
    func play(link: String) {
        guard let url = URL(string: link) else { return }
        let playerItem = AVPlayerItem(url: url)
        player = AVPlayer(playerItem: playerItem)
        player?.play()
        isPlaying = true // If I comment this line, the songs list in viewModel does not changes
    }
}

提前致谢!

更新:仍然无法使用

struct SongListView: View {

    @ObservedObject var model: SongListViewModel

    var body: some View {
        // View
    }
}

struct CategoryListView: View {
    var categoryData : [Category]
    @ObservedObject var player: Player

    var body: some View {
        List(categoryData, id: \.id) { category in
            if category.id == 3 {
                NavigationLink(destination: SongListView(model: SongListViewModel(), player: self.player)) {
                    TitleRowView(title: category)
                }
            }

        }
    }
}

最佳答案

SwiftUI视图是结构，因此是不可变的。当您更新状态并导致视图重绘时，它实际上会创建视图的新实例。

在SongListView中，您有

@ObservedObject var model: SongListViewModel = SongListViewModel()

这意味着每次重新绘制SongListView时(包括更改player.isPlaying的任何时间)，您都在使用新的model实例初始化SongListViewModel。

您应该删除默认值，并通过参数将模型提供给SongListView的初始化程序-

@ObservedObject var model: SongListViewModel