当 SwiftUI 视图被关闭时，如何发送最后一条消息并关闭套接字？

Question

我有一个 SwiftUI 工作表视图，其中有一个处理 tcp 通信的 ObservedObject，当此工作表被关闭时，我需要它发送最后一条 tcp 消息，然后关闭套接字. onDisappear 事件似乎永远不会被触发（编辑：找到了罪魁祸首，因为我使用 UIHostingController 呈现工作表，仍然需要解决方案) 我已经尝试将它放在表单、导航视图中，尝试为其创建一个新堆栈，但没有任何效果。因此，我尝试使用我的 ObservedObject deinit，但是如果我在关闭视图后尝试快速重新打开视图，则会出现错误的访问错误。

deinit {
    let msg = getUpdatedTimersString()
    self.connection.sendMsg(msg, success: connection.close)
}

来自我使用Network Framework的连接类

func sendMsg(_ message: String, success: @escaping () -> Void = { }, error: @escaping () -> Void = { }) {
        let msg = message + "\r\n"
        let data: Data? = msg.data(using: .utf8)
        debugPrint("Sending: \(msg)")
        connection.send(content: data, completion: .contentProcessed { (sendError) in
            if let sendError = sendError {
                self.debug("\(sendError)")
                error()
            } else {
                success()
            }
        })
}

func close() {
        connection.cancel()
}

编辑：在下面添加视图代码

struct ScheduleView: View {
    @ObservedObject var scheduleManager = ScheduleManager() // This handles the tcp communication, the deinit you see above is from this

    var body: some View {
        NavigationView {
            Form {
                ForEach(scheduleManager.timers) { timer in
                    ScheduleForm(scheduleManager: self.scheduleManager, timer: timer).onDisappear { debugPrint("schedule form row disappeared") } // This is just a view that adds a section header and a DatePicker to the form for each timer
                }
            }.onDisappear { debugPrint("form disappeared") }

            .navigationBarTitle(Text("Schedule"), displayMode: .inline)
        }.onDisappear() { debugPrint("nav disappeared") }
    }
}

这些 onDisappear 都不适合我，ScheduleForm 行中的行是唯一一个甚至对我触发的行，但它会在创建工作表时触发每次我将一行滚动到视线之外，但在我关闭工作表时不会。

Answer 1

解决办法：

final class ScheduleController: UIHostingController<ScheduleView> {
    required init?(coder: NSCoder) {
        super.init(coder: coder, rootView: ScheduleView())
    }

    init() {
        super.init(rootView: ScheduleView())
    }
    override func viewWillDisappear(_ animated: Bool) {
        rootView.scheduleManager.updateTimers() // this sends the last message
    }

    override func viewDidDisappear(_ animated: Bool) {
        rootView.scheduleManager.connection.close // this closes the connection
    }
}

Answer 2

我做的第一件事是改变你的函数签名，使用一个闭包来完成成功和错误。

func sendMsg(_ message: String, completion: ((Bool) ->())? = nil)

然后我们可以在 onDisappear 修饰符中使用它。完成后关闭连接。

struct ContentView: View {

  var body: some View {

    Text("Hello World").onDisappear {
      sendMsg("last msg", completion: { completed in
        close()
      })
    }

  }
}

Answer 3

我经常做的事情是这样的：

struct ScheduleView: View {

@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>

@ObservedObject var scheduleManager = ScheduleManager() 

var body: some View {
    NavigationView {
        Form {
            ForEach(scheduleManager.timers) { timer in
                ScheduleForm(scheduleManager: self.scheduleManager, timer: timer)
            }
        }
    }.onDisappear(perform: doExit)
     .navigationBarTitle(Text("Schedule"), displayMode: .inline)
}

func doExit() {

  // do your closing etc ... here

  // then to go back to the previous view
  self.presentationMode.wrappedValue.dismiss()
}

}

Answer 4

我有这个非常粗略的测试工作。 显示一个工作表，当您滑动时，会触发 onDisappear 并执行 doExit 函数。对 UIHostingController 一无所知。

struct ContentView: View {
@State var testArray = ["one", "two", "three"]
@State var showMe = false

var body: some View {
    Button(action: { self.showMe = true}) {
        Text("Press button")
    }.sheet(isPresented: $showMe, onDismiss: {self.showMe = false}) { TestView(scheduleManager: self.testArray) }
}
}

struct TestView: View {
@Environment(\.presentationMode) var presentationMode: Binding<PresentationMode>
@State var scheduleManager: [String]

var body: some View {
    NavigationView {
        Form {
            ForEach(scheduleManager, id: \.self) { timer in
                Text(timer)
            }
        }
    }.onDisappear(perform: doExit)
}

func doExit() {
    print("-----> TestView doExit")
    // then to go back to the previous view
    self.presentationMode.wrappedValue.dismiss()
}
}