如何编写Swift 3中的延迟

谁践踏了优雅 2022-11-28 10:33 68阅读 0赞

本文翻译自：[How to program a delay in Swift 3][]

*In earlier versions of Swift, one could create a delay with the following code:* **在早期版本的Swift中，可以使用以下代码创建延迟：**

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
    }

*But now, in Swift 3, Xcode automatically changes 6 different things but then the following error appears: "Cannot convert `DispatchTime.now` to expected value `dispatch_time_t` aka `UInt64` ."* **但是现在，在Swift 3中，Xcode会自动更改6个不同的内容，但随后出现以下错误：“无法将`DispatchTime.now`转换为期望值`dispatch_time_t`又名`UInt64` 。”**

*How can one create a delay before running a sequence of code in Swift 3?* **如何在Swift 3中运行一系列代码之前创建延迟？**

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### \#1楼 ###

参考：[https://stackoom.com/question/2zzDr/如何编写Swift-中的延迟][https_stackoom.com_question_2zzDr_Swift-]

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### \#2楼 ###

*After a lot of research, I finally figured this one out.* **经过大量的研究，我终于想到了这个。**

DispatchQueue.main.asyncAfter(deadline: .now() + 2.0) { // Change `2.0` to the desired number of seconds.
       // Code you want to be delayed
    }

*This creates the desired "wait" effect in Swift 3 and Swift 4.* **这在Swift 3和Swift 4中创建了所需的“等待”效果。**

*Inspired by a part of [this answer][] .* **灵感来自[这个答案][this answer]的一部分。**

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### \#3楼 ###

*Try the following function implemented in **Swift 3.0 and above*** **尝试在Swift 3.0及更高版本中实现的以下功能**

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

*Usage* **用法**

delayWithSeconds(1) {
       //Do something
    }

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### \#4楼 ###

*I like one-line notation for GCD, it's more elegant:* **我喜欢GCD的单行表示法，它更优雅：**

DispatchQueue.main.asyncAfter(deadline: .now() + 42.0) {
            // do stuff 42 seconds later
        }

*Also, in iOS 10 we have new Timer methods, eg block initializer:* **此外，在iOS 10中我们有新的Timer方法，例如块初始化器：**

*(so delayed action may be cancelled)* **（因此可能会取消延迟行动）**

let timer = Timer.scheduledTimer(withTimeInterval: 42.0, repeats: false) { (timer) in
            // do stuff 42 seconds later
        }

*Btw, keep in mind: by default, timer is added to the default run loop mode.* ***顺便说一句，请记住：默认情况下，计时器被添加到默认的运行循环模式。*** *It means timer may be frozen when this loop mode is on hold (for example, when scrolling a UIScrollView) You can solve this issue by adding the timer to the specific run loop mode:* ***这意味着当此循环模式处于保持状态时（例如，滚动UIScrollView时）可能会冻结计时器。您可以通过将计时器添加到特定的运行循环模式来解决此问题：***

RunLoop.current.add(timer, forMode: .commonModes)

*At this [blog post][] you can find more details.* ***在这篇[博文中，][blog post]您可以找到更多详细信息。***

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### \#5楼 ###

*//Runs function after x seconds* **//在x秒后运行功能**

public static func runThisAfterDelay(seconds: Double, after: @escaping () -> Void) {
        runThisAfterDelay(seconds: seconds, queue: DispatchQueue.main, after: after)
    }
    
    public static func runThisAfterDelay(seconds: Double, queue: DispatchQueue, after: @escaping () -> Void) {
        let time = DispatchTime.now() + Double(Int64(seconds * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC)
        queue.asyncAfter(deadline: time, execute: after)
    }

*//Use:-* **//使用：-**

runThisAfterDelay(seconds: x){
      //write your code here
    }

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### \#6楼 ###

*Try the below code for delay* **请尝试以下代码进行延迟**

//MARK: First Way
    
    func delayForWork() {
        delay(3.0) {
            print("delay for 3.0 second")
        }
    }
    
    delayForWork()

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// MARK: Second Way
    
    DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
        // your code here delayed by 0.5 seconds
    }

[How to program a delay in Swift 3]: https://oldbug.net/q/2zzDr/How-to-program-a-delay-in-Swift-3
[https_stackoom.com_question_2zzDr_Swift-]: https://stackoom.com/question/2zzDr/%E5%A6%82%E4%BD%95%E7%BC%96%E5%86%99Swift-%E4%B8%AD%E7%9A%84%E5%BB%B6%E8%BF%9F
[this answer]: https://stackoverflow.com/a/24034838/5700898
[blog post]: http://bynomial.com/blog/?p=67