swift - 在 MVVM 架构中实现 NSTimer

Question

我想实现一个 NSTimer 来使用 NSTimeInterval 显示一个计时器，所以我环顾四周，找到了这段代码，我将它放入了我的 ViewModel 层:

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 View 中显示当前耗时，所以尝试了这个但没有成功:

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

如何在我的 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，也可以提供一个闭包，当它具有字符串值时 updateTime 将调用该闭包。