Swift 3.0版本

以下闭包函数在主线程上执行一些延迟后的任务。

func performAfterDelay(delay : Double, onCompletion: @escaping() -> Void){

    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delay, execute: {
       onCompletion()
    })
}

像这样调用这个函数:

performAfterDelay(delay: 4.0) {
  print("test")
}

对于多个函数使用这个。这对于静态函数或任何UI更新使用动画或活动加载器非常有帮助。

DispatchQueue.main.asyncAfter(deadline: .now() + 0.9) {
            // Call your function 1
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                // Call your function 2
            }
        }

例如-在tableView重新加载之前使用动画。或任何其他UI更新后的动画。

*// Start your amination* 
self.startAnimation()
DispatchQueue.main.asyncAfter(deadline: .now() + 0.9) {
                *// The animation will execute depending on the delay time*
                self.stopAnimation()
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                    *// Now update your view*
                     self.fetchData()
                     self.updateUI()
                }
            }

Swift 3和4:

您可以在DispatchQueue上创建一个扩展，并在内部添加使用DispatchQueue asyncAfter函数的函数delay

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

使用:

DispatchQueue.delay(.seconds(1)) {
    print("This is after delay")
}

在Swift 3.0中

调度队列

  DispatchQueue(label: "test").async {
        //long running Background Task
        for obj in 0...1000 {
            print("async \(obj)")
        }

        // UI update in main queue
        DispatchQueue.main.async(execute: { 
            print("UI update on main queue")
        })

    }

    DispatchQueue(label: "m").sync {
        //long running Background Task
        for obj in 0...1000 {
            print("sync \(obj)")
        }

        // UI update in main queue
        DispatchQueue.main.sync(execute: {
            print("UI update on main queue")
        })
    }

5秒后调度

    DispatchQueue.main.after(when: DispatchTime.now() + 5) {
        print("Dispatch after 5 sec")
    }

使用这段代码在2.0秒后执行一些UI相关的任务。

            let delay = 2.0
            let delayInNanoSeconds = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)))
            let mainQueue = dispatch_get_main_queue()

            dispatch_after(delayInNanoSeconds, mainQueue, {

                print("Some UI related task after delay")
            })

Swift 3.0版本

以下闭包函数在主线程上执行一些延迟后的任务。

func performAfterDelay(delay : Double, onCompletion: @escaping() -> Void){

    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + delay, execute: {
       onCompletion()
    })
}

像这样调用这个函数:

performAfterDelay(delay: 4.0) {
  print("test")
}

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
 }
}