Swift 中超级简单的尾随闭包语法

Question

我正在尝试跟随 example in the Swift docs 进行尾随闭包。

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，函数没有被调用。以上有什么问题吗？

这是 Apple 示例：

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

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

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

Answer 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时，最后 return 像这样的响应

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

并打电话给

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

Answer 2

这是您修复的示例：

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

Swift 中超级简单的尾随闭包语法

Super simple trailing closure syntax in Swift

closures

trailing

ios

swift