我收到此错误 ->Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)随机的。我不太明白它到底是什么时候发生的。大多数时候是在视图刷新时。错误出现在以下行：group.leave()被处决。
我想做什么： 我想从我的 firebase 数据库中获取带有图像、名称和歌曲的专辑，这些专辑也有名称和图像。我检查了这些值，据我所知，它们都没有问题。但当试图向他们展示时，展示的内容是随机的。有时一切都是对的，有时一张专辑展示了两次，有时只展示了一张专辑，有时一张专辑包含另一张专辑的歌曲。
My firebase database has albums stored as documents, each document has albumimage/name and 2 subcollections of "unlocked" with documents(user uid) that store "locked":Bool and "songs" with a document for each song that stores image/name
这是获取我的专辑及其歌曲的函数：
let group = DispatchGroup()
@State var albums: [Album] = []
@State var albumSongs: [AlbumSong] = []
func fetchAlbums() {
FirebaseManager.shared.firestore.collection("albums").getDocuments { querySnapshot, error in
if let error = error {
print(error.localizedDescription)
return
}
guard let documents = querySnapshot?.documents else {
return
}
let uid = FirebaseManager.shared.auth.currentUser?.uid
documents.forEach { document in
let data = document.data()
let name = data["name"] as? String ?? ""
let artist = data["artist"] as? String ?? ""
let releaseDate = data["releaseDate"] as? Date ?? Date()
let price = data["price"] as? Int ?? 0
let albumImageUrl = data["albumImageUrl"] as? String ?? ""
let docID = document.documentID
FirebaseManager.shared.firestore.collection("albums").document(docID)
.collection("songs").getDocuments { querySnapshot, error in
if let error = error {
return
}
guard let documents = querySnapshot?.documents else {
return
}
self.albumSongs = documents.compactMap { document -> AlbumSong? in
do {
return try document.data(as: AlbumSong.self)
} catch {
return nil
}
}
group.leave()
}
FirebaseManager.shared.firestore.collection("albums").document(docID)
.collection("unlocked").document(uid ?? "").getDocument { docSnapshot, error in
if let error = error {
return
}
guard let document = docSnapshot?.data() else {
return
}
group.enter()
group.notify(queue: DispatchQueue.global()) {
if document["locked"] as! Bool == true {
self.albums.append(Album(name: name, artist: artist,
songs: albumSongs, releaseDate: releaseDate, price: price, albumImageUrl: albumImageUrl))
print("albums: ",albums)
}
}
}
}
}
}
我打电话给我的fetchAlbums()在我看来.onAppear()
我的专辑歌曲：
struct AlbumSong: Identifiable, Codable {
@DocumentID var id: String? = UUID().uuidString
let title: String
let duration: TimeInterval
var image: String
let artist: String
let track: String
}
我的专辑：
struct Album: Identifiable, Codable {
@DocumentID var id: String? = UUID().uuidString
let name: String
let artist: String
let songs: [AlbumSong]
let releaseDate: Date
let price: Int
let albumImageUrl: String
}
我尝试研究如何使用异步函数从 firebase 获取数据，但我无法让我的代码工作，并且当我只有一张专辑时，使用dispatchGroup 工作得很好。我希望得到解释这段代码如何与异步一起工作的答案，我真的很长时间以来尽了最大努力自己弄清楚它。我也很想知道 DispatchGroup 究竟发生了什么，以及为什么它可以很好地处理一张专辑，但不能处理多张专辑。
我认为你把一些非常简单的事情变得过于复杂化了async await
首先，您的模型需要一些调整，这可能是您的一些问题的根源。
import Foundation
import FirebaseFirestore
import FirebaseFirestoreSwift
struct AlbumSong: Identifiable, Codable {
//No need to set a UUID `@DocumentID` provides an ID
@DocumentID var id: String?
let title: String
let duration: TimeInterval
var image: String
let artist: String
let track: String
}
struct Album: Identifiable, Codable {
//No need to set a UUID `@DocumentID` provides an ID
@DocumentID var id: String?
let name: String
let artist: String
//Change to var and make nil, the initial decoding will be blank
//If any of the other variables might be optional add the question mark
var songs: [AlbumSong]?
let releaseDate: Date
let price: Int
let albumImageUrl: String
}
然后，您可以创建一项服务来使用 Firestore 完成繁重的工作。
struct NestedFirestoreService{
private let store : Firestore = .firestore()
let ALBUM_PATH = "albums"
let SONG_PATH = "songs"
///Retrieves Albums and Songs
func retrieveAlbums() async throws -> [Album] {
//Get the albums
var albums: [Album] = try await retrieve(path: ALBUM_PATH)
//Get the songs, **NOTE: leaving the array of songs instead of making a separate collection might work best.
for (idx, album) in albums.enumerated() {
if let id = album.id{
albums[idx].songs = try await retrieve(path: "\(ALBUM_PATH)/\(id)/\(SONG_PATH)")
}else{
print("\(album) :: has invalid id")
}
}
//Add another loop for `unlocked` here just like the one above.
return albums
}
///retrieves all the documents in the collection at the path
public func retrieve<FC : Identifiable & Codable>(path: String) async throws -> [FC]{
let querySnapshot = try await store.collection(path)
.getDocuments()
return try querySnapshot.documents.compactMap { document in
try document.data(as: FC.self)
}
}
}
然后您只需在表示层中使用几行代码即可实现它。
import SwiftUI
@MainActor
class AlbumListViewModel: ObservableObject{
@Published var albums: [Album] = []
private let svc = NestedFirestoreService()
func loadAlbums() async throws{
albums = try await svc.retrieveAlbums()
}
}
struct AlbumListView: View {
@StateObject var vm: AlbumListViewModel = .init()
var body: some View {
List(vm.albums, id:\.id) { album in
DisclosureGroup(album.name) {
ForEach(album.songs ?? [], id:\.id){ song in
Text(song.title)
}
}
}.task {
do{
try await vm.loadAlbums()
}catch{
print(error)
}
}
}
}
struct AlbumListView_Previews: PreviewProvider {
static var previews: some View {
AlbumListView()
}
}
如果遇到任何解码错误，请通过将问号添加到类型中来使变量可选，就像我对数组所做的那样。