斯威夫特定時器停止後不重新啓動

我試圖創建這個計時器，當遊戲開始時，它將開始計數。當角色死亡時，它停止。我得到了所有的工作，但我的問題是我無法在下一輪重新啓動它。

這是我的代碼。

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

override func didMoveToView(view: SKView) { 
    let aSelector : Selector = "updateTime" 
    timer = NSTimer.scheduledTimerWithTimeInterval(0.01, target: self, selector: aSelector, userInfo: nil, repeats: true) 
    startTime = NSDate.timeIntervalSinceReferenceDate() 

    scoreLabel.fontName = "Helvetica" 
    scoreLabel.fontSize = 40 
    scoreLabel.text = "0" 
    scoreLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMaxY(self.frame) - 90) 
    scoreLabel.zPosition = 20 

    self.addChild(scoreLabel) 
} 

func updateTime() { 
    var currentTime = NSDate.timeIntervalSinceReferenceDate() 
    var elapsedTime: NSTimeInterval = currentTime - startTime 
    let minutes = UInt8(elapsedTime/60.0) 
    elapsedTime -= (NSTimeInterval(minutes) * 60) 
    let seconds = UInt8(elapsedTime) 
    elapsedTime -= NSTimeInterval(seconds) 
    let fraction = UInt8(elapsedTime * 100) 

    let strMinutes = minutes > 9 ? String(minutes): "0" + String(minutes) 
    let strSeconds = seconds > 9 ? String(minutes): "0" + String(seconds) 
    let strFraction = fraction > 9 ? String(fraction): "0" + String(fraction) 

    scoreLabel.text = "\(strMinutes):\(strSeconds):\(strFraction)" 
} 

func didBeginContact(contact: SKPhysicsContact) { 
    if (gameOver) == 0 { 
     timer.invalidate() 
     gameOver = 1 
     movingObjects.speed = 0 
     gameOverLabel.fontName = "Helvetica" 
     gameOverLabel.fontSize = 40 
     gameOverLabel.text = "Game over! press to restart." 
     gameOverLabel.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame)) 
     gameOverLabel.zPosition = 20 
     labelHolder.addChild(gameOverLabel) 
    } 
} 

override func touchesBegan(touches: Set<NSObject>, withEvent event: UIEvent) { 
    if (gameOver == 0) { 
      my methods...... 
    } else { 
     scoreLabel.text = "00:00:00" 
     gameOver = 0 
    } 
}

來源

2015-10-17 prival