Check if Timer is running

问题

I have been trying to refill in game lives with a timer, but whenever I leave a view and return, the timer duplicates and becomes faster. I have tried to address this with the Timer?.isValid function to only run the timer when it is invalid so it never duplicates, but it cannot seem to check is the timer is invalid in an if statement.

This is the if statement that I have been using so far:

if (myTimer?.isValid){
} else{
//start timer
}

Any help would be appreciated, thanks.

回答1:

I recommend to use self-checking startTimer() and stopTimer() functions, the timer will be started only if it's not currently running, the stop function sets the timer variable reliably to nil.

var timer : Timer?

func startTimer()
{
    if timer == nil {
        timer = Timer.scheduledTimer...
    }
}

func stopTimer()
{
    if timer != nil {
       timer!.invalidate()
       timer = nil
    }
}

回答2:

You need to check if your Timer instance isValid (not the Timer class), let's say: if myTimer.isValid? {}.

来源：https://stackoverflow.com/questions/44423574/check-if-timer-is-running