Swift中的超级简单的尾随闭包语法

Question

我正在尝试遵循example in the Swift docs进行结尾关闭。

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，未调用该函数。上面有什么问题？

这是苹果公司的例子：

  

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

     

//以下是在不使用结尾闭包的情况下调用此函数的方式：

     

someFunctionThatTakesAClosure（关闭：{       //闭包的主体在这里}）

Answer 1

您对文档的解释不够清楚

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()
}  

尾随闭包用于完成请求，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)
   }
}  

并致电

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

您错过阅读的内容

Answer 2

以下是您的固定示例：

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