Question

我读过this一个，但对我来说没有任何理解。但我理解这种闭包语法：

var cal = {(num1: Int)-> Int in
    return num1 * 2;
}

var clusers = [cal,
               {(num1:Int) -> Int in return num1 * 3},
               {(num1:Int) -> Int in num1 * 4},
               {(num1:Int) in num1 * 5},
               { num1 in num1 * 6},
               { $0 * 7}]
for cluser in clusers{
    cluser(100)
}

如何进行尾随关闭？

基本上这是一个尾随闭包。我无法理解：

  //call dispatch async to send a closure to download queue
  dispatch_async(download) { () ->Void in

    //some code goes here          
  }

Answer 1

让这是我的功能

func someFunctionThatTakesAClosure(index: Int, closure: () -> Void) {

}

如果你需要将一个闭包传递给上面的函数，你可以写下面的内容

someFunctionThatTakesAClosure(5, closure: {
   // code included in closure
})

但是如果闭包是传递给函数的最后一个参数，就像在上面的函数中一样，我们可以像上面这样编写一段代码

someFunctionThatTakesAClosure(5) { 
   // code included in closure
}

这就是为什么它被称为尾随闭包。

尾随闭包如何工作？

1 个答案: