SwiftUI：dataTaskPublisherfor：URLRequest冻结，无响应，无错误

问题描述

我正在尝试使用返回JSON的dataTaskPublisher（用于：URLRequest）从Apple Music API中获取数据。然后，我解码数据并将其转换为播放列表。我已经尝试了几种方法，但这是目前的样子。

我有自己的viewmodel，容器和视图：

class LibraryPlaylistviewmodel: ObservableObject {
    @Published private(set) var state = State()
    var subscriptions: Set<AnyCancellable> = Set()
    
    struct State {
        var playlists: [LibraryPlaylist] = []
    }
    
    func getNextOffsetIfAvailable() {
        AppleMusicAPIEnum.fetchGetAllLibraryPlaylists()
            .sink(receiveCompletion: onReceive,receiveValue: onReceive)
            .store(in: &subscriptions)
    }
    
    private func onReceive(_ completion: Subscribers.Completion<Error>) {
        switch completion {
        case .finished:
            break
        case .failure:
            print("something went wrong")
        }
    }
    
    private func onReceive(_ batch: [LibraryPlaylist]) {
        state.playlists += batch
    }
}

struct EndlessListContainer: View {
    @Observedobject var viewmodel: LibraryPlaylistviewmodel
    
    var body: some View {
        EndlessList(
            libraryPlaylists: viewmodel.state.playlists
        )
        .onAppear(perform: viewmodel.getNextOffsetIfAvailable)
    }
}

struct EndlessList: View {
    let libraryPlaylists: [LibraryPlaylist]
    
    var body: some View {
        List {
            ForEach(libraryPlaylists,id: \.uniqueID) { playlist in
                PlaylistRow(playlist: playlist)
            }
        }
    }
    
}

struct PlaylistRow: View {
    let playlist: LibraryPlaylist
    
    var body: some View {
        vstack {
            Text(playlist.attributes.name ?? "").font(.title)
        }
        .frame(idealWidth: .infinity,maxWidth: .infinity,alignment: .center)
    }
}

我用于网络请求的枚举：

enum AppleMusicAPIEnum {
    static let musicAPI = AppleMusicAPI()
    
    static func fetchGetAllLibraryPlaylists() -> AnyPublisher<[LibraryPlaylist],Error> {
        let url = URL(string: "https://api.music.apple.com/v1/me/library/playlists")
        
        print("\(url!)")

        var request = URLRequest(url: url!)
        request.httpMethod = "GET"
        request.addValue("Bearer \(self.musicAPI.developerToken)",forHTTPHeaderField: "Authorization")
        request.addValue(self.musicAPI.getUserToken(),forHTTPHeaderField: "Music-User-Token")
        
        print("Set up request")
        
        return URLSession.shared
            .dataTaskPublisher(for: request)
            .tryMap { try JSONDecoder().decode(AllLibraryPlaylistsResponse<LibraryPlaylist>.self,from: $0.data).data }
            .receive(on: dispatchQueue.main)
            .erasetoAnyPublisher()
    }
}

以及解码JSON的结构：

struct AllLibraryPlaylistsResponse<T: Codable>: Codable {
    let data: [T]
}

struct LibraryPlaylist: Codable {
    let attributes: Attributes
    let href,id,type: String
}

struct LibraryPlaylistAttributes: Codable {
    let canEdit: Bool?
    let attributesDescription: PlaylistDescription?
    let name: String
    let playParams: PlaylistPlayParams

    enum CodingKeys: String,CodingKey {
        case canEdit
        case attributesDescription = "description"
        case name,playParams
    }
}

struct PlaylistDescription: Codable {
    let standard: String?
}

struct PlaylistPlayParams: Codable {
    let id: String?
    let isLibrary: Bool?
    let kind: String?
}

然后我有了一个带有NavigationLink的视图，我用它来打开包含如下播放列表的视图：

NavigationLink(destination: EndlessListContainer(viewmodel: LibraryPlaylistviewmodel())) {
     // Content
}

点击NavigationLink后，它会高亮显示，并且应用程序会无限期挂起，而不会切换到新视图。

我知道我输入fetchGetAllLibraryPlaylists()是因为可以打印该URL，但出于某种原因print("Set up request")却没有。我以前曾将此URLRequest与dataTask(with request: URLRequest)配合使用良好，所以我认为并非如此。

想知道我哪里做错了，还有没有更简洁的方法呢？

解决方法

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