SwiftUI异步网络请求后@State值不更新，无法更新DetailView数据

你的核心问题在于：League是值类型（struct），当你在ViewModel里更新leagues数组中某个League的seasons时，DetailView里的@State var league是独立的副本，不会自动同步ViewModel中数组里的最新数据。另外，ChangeButton切换联赛时，虽然通过Binding更新了DetailView的league，但这个新的league同样是ViewModel数组里的副本，后续ViewModel更新该league的seasons时，DetailView的副本还是不会同步。

我们需要让DetailView直接依赖ViewModel中的数据源，而不是维护自己的@State副本。具体修改如下：

1. 修改DetailView，用联赛ID追踪选中项 #

移除@State var league，改用@State var selectedLeagueId，通过ID从ViewModel的数组中实时获取最新的联赛数据：

struct DetailView: View {
    @EnvironmentObject var vm: LeagueViewModel
    @State var selectedLeagueId: String
    
    // 实时从ViewModel获取当前选中的联赛
    private var currentLeague: League? {
        vm.leagues.first(where: { $0.id == selectedLeagueId })
    }
    
    var body: some View {
        VStack {
            if let league = currentLeague {
                if let unwrappedSeasons = league.seasons {
                    List {
                        ForEach(unwrappedSeasons, id: \.year) { season in
                            Text(season.displayName)
                        }
                    }
                } else {
                    ProgressView()
                }
            } else {
                Text("联赛不存在")
            }
        }
        .onAppear {
            Task {
                try await vm.loadSeasons(forLeague: selectedLeagueId)
            }
        }
        .navigationBarTitle(Text(currentLeague?.name ?? "联赛详情"), displayMode: .inline)
        .toolbar {
            ToolbarItem(placement: .navigationBarTrailing) {
                ChangeButton(selectedLeagueId: $selectedLeagueId)
            }
        }
    }
}

2. 修改ChangeButton，绑定联赛ID #

不再绑定League实例，而是绑定ID，切换时直接更新ID，让DetailView自动获取最新数据：

struct ChangeButton: View {
    @EnvironmentObject var vm: LeagueViewModel
    @Binding var selectedLeagueId: String
    
    var body: some View {
        Menu {
            ForEach(vm.leagues) { league in
                Button {
                    self.selectedLeagueId = league.id
                } label: {
                    Text(league.name)
                }
            }
        } label: {
            Image(systemName: "calendar")
        }
    }
}

3. 更新ContentView的导航链接传递ID #

把原来传递League实例改成传递ID：

struct ContentView: View {
    @StateObject var vm = LeagueViewModel()
    
    var body: some View {
        NavigationView {
            VStack {
                if vm.leagues.isEmpty {
                    ProgressView()
                } else {
                    List {
                        ForEach(vm.leagues) { league in
                            NavigationLink(destination: DetailView(selectedLeagueId: league.id)) {
                                Text(league.name)
                            }
                        }
                    }
                }
            }
            .navigationBarTitle(Text("联赛列表"), displayMode: .large)
        }
        .environmentObject(vm)
    }
}

额外优化：确保ViewModel更新触发视图刷新 #

因为League是struct，修改数组中元素的内部属性时，数组本身的引用不会变化，@Published可能无法触发刷新。修改loadSeasons方法，通过替换整个元素来确保通知发出：

func loadSeasons(forLeague id: String) async throws {
    let (data, _) = try await URLSession.shared.data(from: URL(string: "https://api-football-standings.azharimm.site/leagues/\(id)/seasons")!)
    guard let seasons = try? JSONDecoder().decode(SeasonResponse.self, from: data) else {
        throw URLError(.cannotParseResponse)
    }
    await MainActor.run {
        if let responsedLeagueIndex = leagues.firstIndex(where: { $0.id == id }),
           let unwrappedSeasons = seasons.data?.seasons {
            // 创建新的League实例替换原数组中的元素
            var updatedLeague = leagues[responsedLeagueIndex]
            updatedLeague.seasons = unwrappedSeasons
            leagues[responsedLeagueIndex] = updatedLeague
            print(unwrappedSeasons)
        }
    }
}

• @State var league是DetailView内部的状态，是ViewModel中league的值拷贝，ViewModel更新数组里的league时，这个拷贝不会自动同步。
• 用@Binding传递拷贝给ChangeButton，切换时只是把另一个league的拷贝赋值给它，依然和ViewModel的数据源脱节。

改用ID追踪后，DetailView始终从ViewModel的leagues数组中获取数据，ViewModel的数据更新会自动触发视图刷新，完美解决异步更新后的同步问题。

内容的提问来源于stack exchange，提问作者Nizami