在結構中使用類會出現錯誤：“不允許部分應用‘變異’方法”-有解無憂

我正在一個結構中創建一個類來創建一個在 Apple Watch 和配對手機之間發送資訊的計時器。嘗試使用按鈕運行計時器時出現錯誤：

不允許部分應用“變異”方法

我創建類的方式如下：

import SwiftUI

struct ContentView: View {

    //Timer to send information to phone
    var timerLogic: TimerLogic!
    
    var body: some View {
        
            Button(action: startTimer, //"partial application of 'mutating' method is not allowed"
                   label: {
                Image(systemName: "location")
            })
    }
      
   // Class with the timer logic
    class TimerLogic {
        var structRef: ContentView!
        var timer: Timer!
        
        init(_ structRef: ContentView) {
            self.structRef = structRef
            self.timer = Timer.scheduledTimer(
                timeInterval: 3.0,
                target: self,
                selector: #selector(timerTicked),
                userInfo: nil,
                repeats: true)
        }
        
        func stopTimer() {
            self.timer?.invalidate()
            self.structRef = nil
        }
        
        // Function to run with each timer tick
        @objc private func timerTicked() {
            self.structRef.timerTicked()
        }
    }
    
    mutating func startTimer() {
        self.timerLogic = TimerLogic(self)
    }
    
   // Function to run with each timer tick, this can be any action
    func timerTicked() {
        let data = ["latitude": "\(location.coordinate.latitude)", "longitud": "\(location.coordinate.longitude)"]
        
        connectivity.sendMessage(data)
    }
}

可能解決錯誤的最接近的解決方案是這個還是有另一個？

uj5u.com熱心網友回復：

SwiftUIView不應該有mutating屬性/功能。相反，他們應該使用屬性包裝像@State與@StateObject國有。

除了mutating功能之外，您還與 SwiftUI 的原則發生了沖突。例如，您永遠不應該嘗試保留對 a 的參考View并在其上呼叫函式。視圖在 SwiftUI 中是暫時的，如果您需要回呼它們，不應期望它們再次存在。此外，SwiftUI 傾向于與 Combine 攜手并進，這將非常適合在您的Timer代碼中實作。

這可能是一個合理的重構：

import SwiftUI
import Combine

// Class with the timer logic
class TimerLogic : ObservableObject {
    @Published var timerEvent : Timer.TimerPublisher.Output?
    private var cancellable: AnyCancellable?
    
    func startTimer() {
        cancellable = Timer.publish(every: 3.0, on: RunLoop.main, in: .default)
            .autoconnect()
            .sink { event in
                self.timerEvent = event
            }
    }
    
    func stopTimer() {
        cancellable?.cancel()
    }
}

struct ContentView: View {
    
    //Timer to send information to phone
    @StateObject var timerLogic = TimerLogic()
    
    var body: some View {
        Button(action: timerLogic.startTimer) {
            Image(systemName: "location")
        }
        .onChange(of: timerLogic.timerEvent) { _ in
            timerTicked()
        }
    }
    
    // Function to run with each timer tick, this can be any action
    func timerTicked() {
        print("Timer ticked...")
        //...
    }
}

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