Swift Function & Closure

概述Functions Functions are self-contained chunks of code that perform a specific task. You give a function a name that identifies what it does, and this name is used to “call” the function to perform its

Functions

Functionsare self-contained chunks of code that perform a specific task. You give a function a name that IDentifIEs what it does,and this name is used to “call” the function to perform its task when needed.

函数是以一个用来执行特殊任务的自包含代码块

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Functions.html#//apple_ref/doc/uid/TP40014097-CH10-ID158

Closures:

@H_403_44@Closuresare self-contained blocks of functionality that can be passed around and used in your code. Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages.

和函数一样也就是代码块，和C，OC里面的block相似，和其他语言的匿名函数相似

https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html#//apple_ref/doc/uid/TP40014097-CH11-ID94

表达式如下:

{ (parameters) -> return type in

    statements

}

Global 和nested函数实际上是closure的特例:

Global函数:一个有名字但不获取任何值的closure

nested函数:有名字，同时能够获取到他们enclosing function里的值

Closure 式子:一个轻量级语法书写的没有名字的closure，同时能够获取到他所处的 context中的值

这边有个例子

//csdn 竟然没有swift这个语言的标签＝＝

    // 点击 *** 作按钮    @IBAction func operate(sender: UIbutton) {        let operation = sender.currentTitle!        if isUserInMIDdleOfTyPingNumber {            enter()        }        switch operation {        case "×":performOperation { 
func someFunctionThatTakesAClosure(closure: () -> ()) {    // function body goes here} // here's how you call this function without using a trailing closure: someFunctionThatTakesAClosure({    // closure's body goes here}) // here's how you call this function with a trailing closure instead: someFunctionThatTakesAClosure() {    // trailing closure's body goes here}
 *  } // Trailing closure 这边传入的其实是 function type 这个nested function就可以直接这么写了        case "÷":performOperation {  /  }        case "+":performOperation {  +  }        case "−":performOperation {  -  }        case "√":performOperationSqrt { sqrt()}        default: break        }    }        //  function type as Parameter Type    func performOperation(operation: (Double,Double) -> Double) {        if operandStack.count >= 2 {            displayValue = operation(operandStack.removeLast(),operandStack.removeLast())            enter()        }    }

之前一直看不懂这语法，今天来解释下

function 和closure分别有Trailing functions 和 Trailing Closures

//含义为 如果你要传一个closure Expression或 function type给function，当作它最后的一个参数时，你可以这么写

// 如果啊 你要传的这个closure Expression是这个function唯一的argument，你连这a pair ofparentheses （）都不用写！！！ 总结

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