NSTimer: floating point value can not be converted

问题:

My code returns the error: fatal error: floating point value can not be converted to UInt8 because it is greater than UInt8.max. The code is being called when a button is pressed (in a different swift file) but I know that the problem wasn't with calling the function so I didn't include it.

code:

//starts the timer
func startTimer(sender: AnyObject)
{
if !timer.valid
{
    timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: sender, selector:     Selector(updateTime()), userInfo: nil, repeats: true)
    startTime = NSDate.timeIntervalSinceReferenceDate()
    //disp = timerDisplay
}
}

//function that configures the timer
func updateTime()
{
var currentTime = NSDate.timeIntervalSinceReferenceDate()

//find the difference between the current time and the start time
var elapsedTime: NSTimeInterval = currentTime - startTime

//calculate the seconds in elapsed time
let seconds = UInt8(elapsedTime)
elapsedTime -= NSTimeInterval(seconds)

///find out the fraction of milliseconds to be displayed
let fraction = UInt8(elapsedTime * 10)

//add the leading zero for minutes, seconds and millseconds and store them as string constants
//let strMinutes = minutes > 9 ? String(minutes):"0" + String(minutes)
let strSeconds = seconds > 9 ? String(seconds):"0" + String(seconds)
let strFraction = fraction > 9 ? String(fraction):"0" + String(fraction)

//display the time left to a string
timerDisplay = "\(strSeconds):\(strFraction)"
}

func stopTimer()
{
timer.invalidate()
}

回答1:

I would take a different approach at it since you will need to represent NSTimeInterval many times, so you should consider adding a read-only computed property as an extension to your project to return a string representation of it as follow:

extension NSTimeInterval {
    var time:String {
        return String(format:"%d:%02d:%02d.%02d", Int(self/3600.0), Int((self/60.0) % 60), Int((self) % 60 ), Int(self*100 % 100 ))
    }
}

class ViewController: UIViewController {
    //declarations
    @IBOutlet weak var tappedLabel: UILabel!
    @IBOutlet weak var timerLabel: UILabel!

    var startTime = NSTimeInterval()
    var timer = NSTimer()

    //starts the timer
    func startTimer(sender: AnyObject) {
        if !timer.valid {
            timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: sender, selector: "updateTime", userInfo: nil, repeats:true)
            startTime = NSDate.timeIntervalSinceReferenceDate()
        }
    }
    // calculates the elapsed time in seconds (Double = NSTimeInterval).extension NStimeInterval
    func updateTime() {
        //find the difference between the current time and the start time and return a string out of it
                // updates the text field
        timerLabel.text = (NSDate.timeIntervalSinceReferenceDate() - startTime).time
    }

回答2:

UNint8 can only store values up to 64k (64*1024). If the bucket is full you can't stuff any more into it. Use a larger bucket Int will cope with zillions of digits.