ksnowlv

回顾过去,总结以往;立足现在,铭记当下;技术为主,笔记而已.

Swift闭包

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一.swift中闭包

swift中的闭包格式

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{ (parameters) -> return type in
    statements
}

1. swift block, without any arguments and without return value

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 typealias funcBlockA = () -> ()
 typealias funcBlockAA = () -> Void

var _funcBlockA:funcBlockA = {

    () -> Void in

    println("***block without any arguments and without return value")
}

2.swift block with arguments and return value

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var _funcBlockB:funcBlockB = {
    (stringA:String, stringB:String) ->String in

    println("***swift block with arguments and without any return value")

    return (stringA + stringB)
}

3.swift block with arguments and return value as function

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var _funcBlockC:funcBlockC = {

    (stringA:String, stringB:String) ->(String)->() in

    blockC("***wift block with arguments and  return value:\(stringA) and \(stringB)")
    return blockC
}

4.swift block as function parameter and return value as function with parameter and return value

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var _funcBlockD:funcBlockD = {
    (stringA:String, stringB:String) ->(String)->(String) in

    blockD("***swift block as function parameter:\(stringA) and \(stringB)")
    return blockD
}

二.示例

1.示例代码

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func blockC(name:String)  {

    println(" blockC= (\(name))")
}

func blockD(name:String)->String  {
    var result:String = "blockD = " + name

    println(result)

    return result;
}

class QBlock{

    //swift block, without any arguments and without return value
    typealias funcBlockA = () -> ()
    typealias funcBlockAA = () -> Void
    //swift block with arguments and return value
    typealias funcBlockB = (String, String) -> String
    //swift block with arguments and  return value as function
    typealias funcBlockC = (String, String) -> (String)->()
    //swift block as function parameter and  return value as function with parameter and return value
    typealias funcBlockD = (String, String) -> (String)->String

    var _funcBlockA:funcBlockA = {

        () -> Void in

        println("***block without any arguments and without return value")
    }

    var _funcBlockB:funcBlockB = {
        (stringA:String, stringB:String) ->String in

        println("***swift block with arguments and without any return value")

        return (stringA + stringB)
    }

    var _funcBlockC:funcBlockC = {

        (stringA:String, stringB:String) ->(String)->() in

        blockC("***wift block with arguments and  return value:\(stringA) and \(stringB)")
        return blockC
    }

    var _funcBlockD:funcBlockD = {
        (stringA:String, stringB:String) ->(String)->(String) in

        blockD("***swift block as function parameter:\(stringA) and \(stringB)")
        return blockD
    }


    init(){
        self.testMemberBlock()
    }

   private func testMemberBlock(){

        ///1. swift block, without any arguments and without return value
        self._funcBlockA()
        //swift block with arguments and without any return value
        var res =  self._funcBlockB("ksnowlv", "kair")
        println("_funcBlockB = result = \(res)")


        // //swift block with arguments and  return value as function
        var blockC  = self._funcBlockC("ksnowlv", "kair")
        blockC("go shopping")

        //swift block as function parameter and  return value as function with parameter and return value
        var blockD  = self._funcBlockD("ksnowlv", "kair")
        var result =  blockD("go shopping")
        println("result blockD = \(result)")
    }
}

2.调用

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var block = QBlock()

objective-c

3.日志

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***block without any arguments and without return value
***swift block with arguments and without any return value
_funcBlockB = result = ksnowlvkair
 blockC= (***wift block with arguments and  return value:ksnowlv and kair)
 blockC= (go shopping)
blockD = ***swift block as function parameter:ksnowlv and kair
blockD = go shopping
result blockD = blockD = go shopping

三.小结

  • 1.与objective-c中的闭包在使用方法上类似，大体上相同，语法格式上的差异。
  • 2.在内存管理方面:objective-c中需要注意循环引用导致的内存泄漏。而swift依然需要注意该问题。

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