Swift 中超级简单的尾随闭包语法答案

【问题标题】：Super simple trailing closure syntax in SwiftSwift 中超级简单的尾随闭包语法
【发布时间】：2019-08-14 00:11:57
【问题描述】：

我正在尝试关注example in the Swift docs 进行尾随关闭。

这是函数：

func someFunctionThatTakesAClosure(closure: () -> Void) {
    // function body goes here
    print("we do something here and then go back")//does not print
}

我在这里称呼它。

        print("about to call function")//prints ok
        someFunctionThatTakesAClosure(closure: {
            print("we did what was in the function and can now do something else")//does not print
        })
        print("after calling function")//prints ok

但是，该函数没有被调用。以上有什么问题？

这是苹果的例子：

func someFunctionThatTakesAClosure(closure: () -> Void) { // 函数体放在这里 }

// 下面是如何在不使用尾随闭包的情况下调用此函数：

someFunctionThatTakesAClosure(闭包：{ // 闭包的主体放在这里 })

【问题讨论】：

闭包只是一个值。就像任何其他值一样，您可以“忽略”它的存在并且什么都不会发生。让任何事情发生都需要您实际使用该值。

标签： ios swift closures trailing

【解决方案1】：

文档对您需要的解释不是很清楚

print("1")
someFunctionThatTakesAClosure() {  // can be also  someFunctionThatTakesAClosure { without ()
    print("3") 

}

func someFunctionThatTakesAClosure(closure: () -> Void) { 
   print("2") 

   /// do you job here and line blow will get you back
    closure()
}

尾随闭包用于完成，例如当您执行网络请求并最终返回这样的响应时

func someFunctionThatTakesAClosure(completion:  @escaping ([String]) -> Void) { 
   print("inside the function body") 
   Api.getData { 
      completion(arr)
   }
}

然后调用

print("Before calling the function")
someFunctionThatTakesAClosure { (arr) in
  print("Inside the function callback  / trailing closure " , arr)
}
print("After calling the function")

你错过了什么

【讨论】：

谢谢，我看到了，但读起来好像你可以使用任何一个。谢谢澄清！我赞成答案。

【解决方案2】：

这是你的例子：

func someFunctionThatTakesAClosure(closure: () -> Void) {
    // function body goes here
    print("we do something here and then go back")

    // don't forget to call the closure
    closure()
}


print("about to call function")

// call the function using trailing closure syntax
someFunctionThatTakesAClosure() {
    print("we did what was in the function and can now do something else")
}

print("after calling function")

输出：

about to call function
we do something here and then go back
we did what was in the function and can now do something else
after calling function

【讨论】：