在實(shí)際編程過程中經(jīng)常需要一個延時操作的功能，下面進(jìn)行一個延時2s的操作

非封裝寫法

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

簡單封裝

• 代碼

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

• 用法

delayWithTime(3) { 
    //your code
}

進(jìn)一步封裝

• 代碼

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

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