Question

我想实现一个NSTimer来显示一个使用NSTimeInterval的计时器，所以我环顾四周找到了这个代码，我把它放到我的ViewModel层中：

public class ViewModel {

public func startTimer() {
    //if !timer.valid {
    timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: #selector(updateTime), userInfo: nil, repeats: true)
    startTime = NSDate.timeIntervalSinceReferenceDate()
    //}
}

@objc public func updateTime() -> String {
    let currentTime = NSDate.timeIntervalSinceReferenceDate()

    //Find the difference between current time and start time.

    var elapsedTime: NSTimeInterval = currentTime - startTime

    //calculate the minutes in elapsed time.

    let minutes = UInt8(elapsedTime / 60.0)

    elapsedTime -= (NSTimeInterval(minutes) * 60)

    //calculate the seconds in elapsed time.

    let seconds = UInt8(elapsedTime)

    elapsedTime -= NSTimeInterval(seconds)

    //add the leading zero for minutes, seconds and millseconds and store them as string constants

    let strMinutes = String(format: "%02d", minutes)
    let strSeconds = String(format: "%02d", seconds)

    //concatenate minuets, seconds and milliseconds as assign it to the UILabel

    return "\(strMinutes):\(strSeconds)"
}
}

我想在我的视图中显示当前已用完的时间，所以尝试了这个但是它不起作用：

viewModel?.startTimer()
timerLabel.text = viewModel?.updateTime()

如何在ViewController标签上显示updateTime()的最新结果？

Answer 1

updateTime方法不能只返回字符串。它必须启动相关标签的更新。您可以对其进行编码以直接更新标签，也可以提供updateTime在具有字符串值时将调用的闭包。

Answer 2

我试图实现Rob的答案，但是无法真正掌握MVVM架构中的CAdisplayLink，并且想出了在不同视图中定期更新GUI元素的相同问题。但是我使用了我的RAC知识并创建并传递了RACSignal来更新我的ViewController：

RACSignal.interval(1.0, onScheduler: .mainThreadScheduler()).subscribeNext({ _ in
                self.timerLabel.text = self.viewModel?.updateTime()
            })

在MVVM体系结构中实现NSTimer

2 个答案: