dispatch_after - GCD在swift？ [英] dispatch_after - GCD in swift?

问题描述

我已经浏览了 iBook 来自Apple，但找不到它的任何定义：

I've gone through the iBook from Apple, and couldn't find any definition of it :

有人可以解释 dispatch_after ？

dispatch_after(<#when: dispatch_time_t#>, <#queue: dispatch_queue_t?#>, <#block: dispatch_block_t?#>)

推荐答案

A更清楚的结构概念：

A clearer idea of the structure:

dispatch_after(when: dispatch_time_t, queue: dispatch_queue_t, block: dispatch_block_t?)

dispatch_time_t 是 UInt64 。 dispatch_queue_t 实际上是 NSObject 的别名，但您应该使用熟悉的GCD方法来获取队列。该块是一个Swift闭包。具体来说， dispatch_block_t 定义为（） - > Void ，相当于（） - > （）。

dispatch_time_t is a UInt64. The dispatch_queue_t is actually type aliased to an NSObject, but you should just use your familiar GCD methods to get queues. The block is a Swift closure. Specifically, dispatch_block_t is defined as () -> Void, which is equivalent to () -> ().

示例用法：

let delayTime = dispatch_time(DISPATCH_TIME_NOW, Int64(1 * Double(NSEC_PER_SEC)))
dispatch_after(delayTime, dispatch_get_main_queue()) {
    print("test")
}

编辑：

我建议使用 @ matt真的很好延迟功能。

I recommend using @matt's really nice delay function.

编辑2：

In Swift 3，将有新的GCD包装器。请参阅此处： https：// github。 com / apple / swift-evolution / blob / master / proposals / 0088-libdispatch-for-swift3.md

In Swift 3, there will be new wrappers for GCD. See here: https://github.com/apple/swift-evolution/blob/master/proposals/0088-libdispatch-for-swift3.md

原始示例将写成如下在Swift 3中：

The original example would be written as follows in Swift 3:

let deadlineTime = DispatchTime.now() + .seconds(1)
DispatchQueue.main.asyncAfter(deadline: deadlineTime) {
    print("test")
}

请注意，您可以将 deadlineTime 声明写为 DispatchTime.now（）+ 1.0 并获得相同的结果，因为 + 运算符被覆盖如下（类似于 - ）：

Note that you can write the deadlineTime declaration as DispatchTime.now() + 1.0 and get the same result because the + operator is overridden as follows (similarly for -):

• func +（time：DispatchTime，seconds：Double） - > DispatchTime


• func +（time：DispatchWalltime，interval：DispatchTimeInterval） - > DispatchWalltime

• func +(time: DispatchTime, seconds: Double) -> DispatchTime
• func +(time: DispatchWalltime, interval: DispatchTimeInterval) -> DispatchWalltime

这意味着如果你不使用 DispatchTimeInterval enum 只需写一个数字，假设你正在使用秒数。

This means that if you don't use the DispatchTimeInterval enum and just write a number, it is assumed that you are using seconds.

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