我经常使用dispatch_after，所以我写了一个顶级实用函数来简化语法:

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

现在你可以这样说:

delay(0.4) {
    // do stuff
}

哇，一种你可以改进的语言。还有什么比这更好的呢?

更新Swift 3, Xcode 8种子6

看起来几乎不值得费心，现在他们已经改进了调用语法:

func delay(_ delay:Double, closure:@escaping ()->()) {
    let when = DispatchTime.now() + delay
    DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}

另一种方法是像这样扩展Double:

extension Double {
   var dispatchTime: dispatch_time_t {
       get {
           return dispatch_time(DISPATCH_TIME_NOW,Int64(self * Double(NSEC_PER_SEC)))
       }
   }
}

然后你可以这样使用它:

dispatch_after(Double(2.0).dispatchTime, dispatch_get_main_queue(), { () -> Void in
            self.dismissViewControllerAnimated(true, completion: nil)
    })

我喜欢matt的延迟函数，但只是出于偏好，我宁愿限制传递闭包。

Swift 4有一个很短的方法来做到这一点:

Timer.scheduledTimer(withTimeInterval: 2, repeats: false) { (timer) in
    // Your stuff here
    print("hello")
}

在Swift 4中

使用以下片段:

    let delayInSec = 1.0
    DispatchQueue.main.asyncAfter(deadline: .now() + delayInSec) {
       // code here
       print("It works")
    }

1)添加这个方法作为UIViewController Extension的一部分。

extension UIViewController{
func runAfterDelay(delay: NSTimeInterval, block: dispatch_block_t) {
        let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
        dispatch_after(time, dispatch_get_main_queue(), block)
    }
}

在VC上调用这个方法:

    self.runAfterDelay(5.0, block: {
     //Add code to this block
        print("run After Delay Success")
    })

2)

performSelector("yourMethod Name", withObject: nil, afterDelay: 1)

3)

override func viewWillAppear(animated: Bool) {

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2), dispatch_get_main_queue(), { () -> () in
    //Code Here
})

/ /紧凑的形式

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2), dispatch_get_main_queue()) {
    //Code here
 }
}

我经常使用dispatch_after，所以我写了一个顶级实用函数来简化语法:

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

现在你可以这样说:

delay(0.4) {
    // do stuff
}

哇，一种你可以改进的语言。还有什么比这更好的呢?

更新Swift 3, Xcode 8种子6

看起来几乎不值得费心，现在他们已经改进了调用语法:

func delay(_ delay:Double, closure:@escaping ()->()) {
    let when = DispatchTime.now() + delay
    DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}