SwiftUI:如何在SwiftUI视图中取消计时器？

struct ContentView: View {
    @State private var timerRunning = true
    
    var body: some View {
        Text("Hello, World!")
            .onAppear {
                startTimer()
            }
            .onDisappear {
                stopTimer()
            }
    }
    
    func startTimer() {
        Timer.scheduledTimer(withTimeInterval: 1, repeats: true) { timer in
            // Timer logic here
            
            // Check if timer should still run
            if !timerRunning {
                timer.invalidate()
            }
        }
    }
    
    func stopTimer() {
        timerRunning = false
    }
}