将参数传递给dispatch_async [英] Passing an argument to dispatch_async

问题描述

我是Swift的新手，看看dispatch_async函数是如何工作的。 API文档显示dispatch_async有两个参数。但是，我能够传递一个参数，这没关系。

I'm new to Swift and looking at how the dispatch_async function works. The API doc shows dispatch_async having two parameters. However, I'm able to pass in one argument and it's okay.

dispatch_async(dispatch_get_main_queue()) { 

}

为什么我不需要传递两个参数？

How come I don't need to pass in two arguments?

谢谢，

Thank you,

API Doc：

推荐答案

这是一个尾随闭包语法

func someFunctionThatTakesAClosure(closure: () -> ()) {
    // function body goes here
}

// here's how you call this function without using a trailing closure:

someFunctionThatTakesAClosure({
    // closure's body goes here
})

// here's how you call this function with a trailing closure instead:

someFunctionThatTakesAClosure() {
    // trailing closure's body goes here
}

https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html

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