倒计时

很多时候会用到倒计时的功能，比如答题PK的App，还有注册时发送验证码

先创建一个timer

timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("fireTimer:"), userInfo: nil, repeats: true)

开启之后，进行计时

 func fireTimer(t : NSTimer!){        if timerStartTime == nil {            timerStartTime = NSDate()            sendCodeBtn.userInteractionEnabled = false                    }        var deltaTime = NSDate().timeIntervalSinceDate(timerStartTime)        var remaintime = 60 - Int(deltaTime + 0.5)        if remaintime <= 0{            self.invalidateTimer()            sendCodeBtn.userInteractionEnabled = true            sendCodeBtn.setTitle("获取验证码", forState: UIControlState.Normal)            sendCodeBtn.layer.borderColor = UIColor.clearColor().CGColor            sendCodeBtn.setTitleColor(UIColor.whiteColor(), forState: UIControlState.Normal)                    }else{            sendCodeBtn.setTitle("\(remaintime)秒后重新获取", forState: UIControlState.Normal)            sendCodeBtn.backgroundColor = UIColor.whiteColor()            sendCodeBtn.layer.borderColor = UIColor.lightGrayColor().CGColor            sendCodeBtn.setTitleColor(UIColor.darkGrayColor(), forState: UIControlState.Normal)                    }            }

注： 主要代码是

var deltaTime = NSDate().timeIntervalSinceDate(timerStartTime)        var remaintime = 60 - Int(deltaTime + 0.5)