ios - 因此，我构建了一个应用程序，该应用程序希望每分钟获得字数。如何使用SwithUI启动ContentView中不存在的计时器

Question

我想启动一个60秒的计时器来测试用户在该分钟内可以键入多少个单词。我开始计算TextField中的字符。但是，现在我需要减少计时器，以便进行数学运算并向用户输出答案。我似乎无法弄清楚计时器不在Content View结构中时如何使用计时器。我可以那样做吗？

import SwiftUI

struct ContentView: View {
    @State var userInput = ""
    @State var modalview = false
    @State var getstarted = false
    @EnvironmentObject var timerHolder : TimerHolder
    var body: some View {

        ZStack() {
            modalView(modalview: $modalview, userInput: userInput)

        }.sheet(isPresented: $modalview) {

        modalView(modalview: self.$modalview)

        }

    }

}




        struct modalView : View {
         @ObservedObject var durationTimer = TimerHolder()

          @Binding var modalview : Bool
            @State var userInput: String = ""


              var body: some View {

                VStack{

                   Button(action: {
                      self.modalview = true
                                 }) {
                                    TextField("Get Started", text:$userInput)
                                        .background(Color.gray)
                                        .foregroundColor(.white)
                                        .frame(width: 300, height: 250)
                                              .cornerRadius(20)

                                    Text("\(userInput.count)")


                                    Text("\(durationTimer.count) Seconds")

                    }

                  }
            }

        }

class TimerHolder : ObservableObject {
var timer : Timer!
@Published var count = 0
func start() {
    self.timer?.invalidate()
    self.count = 0
    self.timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true) {
        _ in
        self.count += 1
        print(self.count)
    }
}






struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView() 
    }
}

}

Answer 1

当您将其作为属性时，最简单的方法是从.onAppear ...开始(当然，假设您在ContentView().environmentObject(TimerHolder())创建时以ContentView传递它)

struct ContentView: View {
    @State var userInput = ""
    @State var modalview = false
    @State var getstarted = false
    @EnvironmentObject var timerHolder : TimerHolder
    var body: some View {

        ZStack() {
            modalView(modalview: $modalview, userInput: userInput)
        }.sheet(isPresented: $modalview) {
           modalView(modalview: self.$modalview)
        }
        .onAppear {
            self.timerHolder.start()
        }
    }
}