swift3.0延时操作

在实际编程过程中经常需要一个延时操作的功能，下面进行一个延时2s的操作

非封装写法

DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 3) { 
      //your code
 }

简单封装

• 代码

public func delayWithTime(_ time: TimeInterval, work: @escaping () -> ()){
    
    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time, execute: work)
}

• 用法

delayWithTime(3) { 
    //your code
}

进一步封装

• 代码

public typealias CancelableTask = ( _ cancel: Bool) -> Void

public func delay( _ time: TimeInterval, work: @escaping () -> ()) -> CancelableTask?{
    
    var finalTask: CancelableTask?
    
    let cancelableTask: CancelableTask = { cancle in
        if cancle {
            finalTask = nil
        } else {
            DispatchQueue.main.async(execute: work)
        }
    }
    
    finalTask = cancelableTask
    
    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time) {
        if let task = finalTask {
            task(false)
        }
    }
    
    return finalTask
}

public func cancel(_ cancelableTask: CancelableTask?) {
    
    cancelableTask?(true)
}

• 用法

 //延时操作
 let task = delay(3) {
      //your code
 }
//取消延时
delay(1.5) { 
     cancel(task)
 }