Swift中的超简单尾随闭包语法

Question

我试图跟随example in the Swift docs进行尾随关闭。

这是功能：

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，该函数未被调用。上面有什么问题？

这是Apple的例子：

func someFunctionThatTakesAClosure（closure :(） - > Void）{//函数体到这里}

//这是你在不使用尾随闭包的情况下调用这个函数的方法：

someFunctionThatTakesAClosure（闭包：{//闭包的身体在这里}）

Answer 1

以下是您修复的示例：

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

Answer 2

Docs对你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响应时

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

打电话

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