计时器改变每场比赛

Question

出于某种原因，当我第一次玩游戏时，一切正常，我的计时器每2秒结束一次。当我第二次再次玩时，它会每隔一秒钟做一次。

var masterTimer: NSTimer? = nil

viewDidLoad中的

：

self.masterTimer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: "First", userInfo: nil, repeats: true)

TimeLeft1等于2，而难度等于3

var TimeLeft1 = defaults.integerForKey("TimeLeft1")
var ScoreType = defaults.integerForKey("ScoreType")
    var Difficulty = defaults.integerForKey("Difficulty")

TimeLeft1 -= 1 //take a second away
    defaults.setInteger(TimeLeft1, forKey: "TimeLeft1")
    if (TimeLeft1 > 0)
    {

    }
    else
    {

        if Difficulty == 1 {
            TimeLeft1 += 5
            defaults.setInteger(TimeLeft1, forKey: "TimeLeft1")
        }
        else if Difficulty == 2 {
            TimeLeft1 += 3
            defaults.setInteger(TimeLeft1, forKey: "TimeLeft1")
        }
        else if Difficulty == 3 {
            TimeLeft1 += 2
            defaults.setInteger(TimeLeft1, forKey: "TimeLeft1")
        }