SwiftUI 的一个技术问题

[wseani]

我有一个需要加载数据的 Task ，想在 View 里显示进度条，但是目前 Task 并不会刷新进度条的值，该怎么做呢？

目前的是

struct ContentView: View {
   @ObservedObject var model: Model

    var body: some View {
        VStack {
            ProgressView("Downloading…", value: model.progress, total: 100)
            .onAppear {
                Task {
                    await model.fetchData()
                }
            }
        }
    }
}



//在 Model.swift 里，代码如下：
@MainActor
class Model: ObservableObject {
    @Published var progress: Int = 0

    func fetchData() async {
        Task {
            do {
                 for idx in 0...100 {
                    progress += 1
                    sleep(1)
                 }
            }
         }
    }
}

[hstdt]

```swift
struct ContentView: View {
@ObservedObject var model: Model = Model()
var body: some View {
VStack {
ProgressView("Downloading…", value: model.progress, total: 100)
.onAppear {
Task {
await model.fetchData()
}
}
}
}
}

class Model: ObservableObject {
@Published var progress: Double = 0
func fetchData() async {
for _ in 0...100 {
await MainActor.run { // 加上 onChange 之后会提示 Publishing changes from background threads is not allowed;
progress += 1
}
sleep(1)
}
}
}
```

[wseani]

@hstdt 多谢，我用类似的方式解决了，代码如下：
```lang-swift
@MainActor
class Model: ObservableObject {
@Published var progress: Int = 0

func fetchData() async {
for idx in 0...100 {
await load_data(idx)
progress += 1
}
}

func load_data() async {
// 加载大文件数据
}
}
```