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
 }
}

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
 }
}

另一个帮手来延迟你的代码，这是100%的Swift使用，并可选地允许选择一个不同的线程来运行你的延迟代码:

public func delay(bySeconds seconds: Double, dispatchLevel: DispatchLevel = .main, closure: @escaping () -> Void) {
    let dispatchTime = DispatchTime.now() + seconds
    dispatchLevel.dispatchQueue.asyncAfter(deadline: dispatchTime, execute: closure)
}

public enum DispatchLevel {
    case main, userInteractive, userInitiated, utility, background
    var dispatchQueue: DispatchQueue {
        switch self {
        case .main:                 return DispatchQueue.main
        case .userInteractive:      return DispatchQueue.global(qos: .userInteractive)
        case .userInitiated:        return DispatchQueue.global(qos: .userInitiated)
        case .utility:              return DispatchQueue.global(qos: .utility)
        case .background:           return DispatchQueue.global(qos: .background)
        }
    }
}

现在你只需在主线程上延迟你的代码，就像这样:

delay(bySeconds: 1.5) { 
    // delayed code
}

如果你想延迟你的代码到不同的线程:

delay(bySeconds: 1.5, dispatchLevel: .background) { 
    // delayed code that will run on background thread
}

如果你喜欢一个框架，也有一些更方便的功能，然后签出handysswift。你可以通过Carthage将它添加到你的项目中，然后像上面的例子一样使用它，例如:

import HandySwift    

delay(bySeconds: 1.5) { 
    // delayed code
}

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)
}

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")
}

以下是Swift中asyncAfter的同步版本:

let deadline = DispatchTime.now() + .seconds(3)
let semaphore = DispatchSemaphore.init(value: 0)
DispatchQueue.global().asyncAfter(deadline: deadline) {
    dispatchPrecondition(condition: .onQueue(DispatchQueue.global()))
    semaphore.signal()
}

semaphore.wait()

与异步的一起:

let deadline = DispatchTime.now() + .seconds(3)
DispatchQueue.main.asyncAfter(deadline: deadline) {
    dispatchPrecondition(condition: .onQueue(DispatchQueue.global()))
}