1.延时执行

//延时1秒执行
let time: TimeInterval = 1.0
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time) { 
    //code
    print("1 秒后输出")
}

2.对延时执行喵神进行了较好的封装，这里我也贴出来了，供大家学习

import Foundation

typealias Task = (_ cancel : Bool) -> Void

func delay(_ time: TimeInterval, task: @escaping ()->()) ->  Task? {

    func dispatch_later(block: @escaping ()->()) {
        let t = DispatchTime.now() + time
        DispatchQueue.main.asyncAfter(deadline: t, execute: block)
    }
    var closure: (()->Void)? = task
    var result: Task?

    let delayedClosure: Task = {
        cancel in
      if let internalClosure = closure {
            if (cancel == false) {
                DispatchQueue.main.async(execute: internalClosure)
            }
        }
        closure = nil
        result = nil
    }

    result = delayedClosure

    dispatch_later {
        if let delayedClosure = result {
            delayedClosure(false)
        }
    }
  return result
}

func cancel(_ task: Task?) {
    task?(true)
}


/*****使用*****/
//调用
delay(2) { print("2 秒后输出") }



//取消
let task = delay(5) { print("拨打 110") }

// 仔细想一想..
// 还是取消为妙..
cancel(task)

3.OC版本

 //延时
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
          //do something 
});