swift - 修改嵌套对象中的状态

Question

我是 Swift 新手，遇到了这个问题。我想在工具栏中制作一个播放/暂停按钮，我决定将工具栏代码移动到它自己的对象Toolbar。该按钮在按下时应该改变其图像，但当我按下它时，状态不会改变。我做错了什么？

struct ContentView: View {
    var body: some View {
        NavigationView {
            List{
                Text("asdf")
            }
            .toolbar {
                Toolbar()
            }
        }
    }
}

struct Toolbar: ToolbarContent {
    @State var started = false
    
    var body: some ToolbarContent {
        ToolbarItem(id:"start-button", placement: .primaryAction) {
            Button(action: {
                self.started.toggle()
            }) {
                Image(systemName: self.started == true ? "pause.fill" : "play.fill")
                    .foregroundColor(.white)
            }
        }
    }
}

Answer 1

使用双向绑定(bind)。

struct ContentView: View {
    @State private var started = false //<-- Here
    
    var body: some View {
        NavigationView {
            List{
                Text("asdf")
            }
            .toolbar {
                Toolbar(started: $started) //<-- Here
            }
        }
    }
}

struct Toolbar: ToolbarContent {
    
    @Binding var started: Bool //<-- Here
    
    var body: some ToolbarContent {
        ToolbarItem(id:"start-button", placement: .primaryAction) {
            Button(action: {
                self.started.toggle()
            }) {
                Image(systemName: self.started ? "pause.fill" : "play.fill")
                    .foregroundColor(.white)
            }
        }
    }
}