DispatchQueue.global(qos: .background).async {
    sleep(4)
    print("Active after 4 sec, and doesn't block main")
    DispatchQueue.main.async{
        //do stuff in the main thread here
    }
}

在Swift 3.0中尝试以下实现

func delayWithSeconds(_ seconds: Double, completion: @escaping () -> ()) {
    DispatchQueue.main.asyncAfter(deadline: .now() + seconds) { 
        completion()
    }
}

使用

delayWithSeconds(1) {
   //Do something
}

你可以创建扩展来轻松使用延迟函数(语法:Swift 4.2+)

extension UIViewController {
    func delay(_ delay:Double, closure:@escaping ()->()) {
        DispatchQueue.main.asyncAfter(
            deadline: DispatchTime.now() + Double(Int64(delay * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC), execute: closure)
    }
}

如何在UIViewController中使用

self.delay(0.1, closure: {
   //execute code
})

Using a dispatch_after block is in most cases better than using sleep(time) as the thread on which the sleep is performed is blocked from doing other work. when using dispatch_after the thread which is worked on does not get blocked so it can do other work in the meantime. If you are working on the main thread of your application, using sleep(time) is bad for the user experience of your app as the UI is unresponsive during that time. Dispatch after schedules the execution of a block of code instead of freezing the thread:

斯威夫特≥ 3.0

let seconds = 4.0
DispatchQueue.main.asyncAfter(deadline: .now() + seconds) {
    // Put your code which should be executed with a delay here
}

Swift≥5.5(异步):

func foo() async {
    try await Task.sleep(nanoseconds: UInt64(seconds * Double(NSEC_PER_SEC)))
    // Put your code which should be executed with a delay here
}

Swift < 3.0

let time = dispatch_time(dispatch_time_t(DISPATCH_TIME_NOW), 4 * Int64(NSEC_PER_SEC))
dispatch_after(time, dispatch_get_main_queue()) {
    // Put your code which should be executed with a delay here
}

在Swift 4.2和Xcode 10.1中

你总共有4种方法来延迟。在这些选项中，首选选项1是在一段时间后调用或执行函数。sleep()是使用最少的情况。

选项1。

DispatchQueue.main.asyncAfter(deadline: .now() + 5.0) {
    self.yourFuncHere()
}
//Your function here    
func yourFuncHere() {

}

第二个选项。

perform(#selector(yourFuncHere2), with: nil, afterDelay: 5.0)

//Your function here  
@objc func yourFuncHere2() {
    print("this is...")
}

选项3。

Timer.scheduledTimer(timeInterval: 5.0, target: self, selector: #selector(yourFuncHere3), userInfo: nil, repeats: false)

//Your function here  
@objc func yourFuncHere3() {

}

选项4。

sleep(5)

如果你想在一段时间后调用一个函数来执行一些东西，不要使用sleep。

这是最简单的

    delay(0.3, closure: {
        // put her any code you want to fire it with delay
        button.removeFromSuperview()   
    })