查看加载时启动NSTimer

Question

我想制作一个简单的时钟应用程序，其中冒号闪烁以使其看起来更好。我的代码到目前为止是：

@IBOutlet weak var clockLabel: UILabel! 
var timerRunning = true 
var timer = NSTimer() 
var OnOff = 0 
var colon = ":" 
var hour = 0 
var minute = 0 

override func viewDidLoad() { 
    super.viewDidLoad() 
    clockLabel.text = ("\(hour)\(colon)\(minute)") 
    timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: "Counting", userInfo: nil, repeats: true) 
} 
override func didReceiveMemoryWarning() { 
    super.didReceiveMemoryWarning() 
} 

func Counting(){ 
    if OnOff == 1 { 
    OnOff = 0 
    colon = ":" 
    clockLabel.text = ("\(hour)\(colon)\(minute)") 
    } 
    if OnOff == 0 { 
    OnOff = 1 
    colon = "" 
    clockLabel.text = ("\(hour)\(colon)\(minute)") 
    } 
} 

我想这样工作的方式是，计时器开始于视图加载的那一刻。我不想按一个按钮来让冒号开始闪烁。 在此先感谢

Answer 1

我没有看到任何问题与您的计时器（您的问题标题另有说明），据我可以告诉它应该在视图加载后每秒触发。

我注意到的一件事是您的代码执行路径中存在一个问题： 如果您更改变量（在第一个中），那么两个随后的if语句重叠，请继续阅读以查看我的解决方案。

稍加改进我会做 - 为OnOff变量似乎是在自然二进制 - 让我们说一个boolean类型：

var colonShown : Bool = false // this is your "OnOff" variable (changed it to be more clear to the reader + made it boolean (you treat it as a boolean, so why not make it boolean?)) 

，然后在你的计时功能（我把它改名为tick()）：

// renamed your Counting() function, no particular reason for that (sorry if that causes confusion) -- you can replace your Counting() function with this one (also make sure to update your timer selector that references the "Counting()" function on each "tick") 
func tick(){ 
    colonShown = !colonShown // toggle boolean value 
    colon = colonShown ? ":" : "" // neat one-liner for your if statement 

    clockLabel.text = ("\(hour)\(colon)\(minute)") 

}