Swift闭包

把Swift中的 block 常见的声明和写法作一个总结。以免后续忘了，好查阅。

//
//  blockDemo.swift
//  swiftDemo
//
//  Created by apple on 14-6-29.
//  Copyright (c) 2014年 fengsh. All rights reserved.
//

import Foundation

//无参无返回值
typealias funcBlock = () -> () //或者 () -> Void
//返回值是String
typealias funcBlockA = (Int,Int) -> String
//返回值是一个函数指针，入参为String
typealias funcBlockB = (Int,Int) -> (String)->()
//返回值是一个函数指针，入参为String 返回值也是String
typealias funcBlockC = (Int,Int) -> (String)->String

class blockDemo
{
    //block作为属性变量
    var blockProperty : (Int,Int) -> String = {a,b in return ""/**/} // 带初始化方式
    var blockPropertyNoReturn : (String) -> () = {param in }

    var blockPropertyA : funcBlockA?  //这写法就可以初始时为nil了,因为生命周其中，(理想状态)可能为nil所以用?
    var blockPropertyB : funcBlockB!  //这写法也可以初始时为nil了,因为生命周其中，(理想状态)认为不可能为nil,所以用!

    init()
    {
        println("blockPropertyA = (blockPropertyA) , blockPropertyB = (blockPropertyB)")
        println("blockProperty = (blockProperty) , blockPropertyNoReturn = (blockPropertyNoReturn)")
    }

    func testProperty(tag:Int)
    {
        switch (tag)
        {
        case 1:
                self.blockPropertyNoReturn("OK GOOD")
        case 2:
                if let exsistBlock = self.blockPropertyA
                {
                    let result = self.blockPropertyA!(7,8)
                    println("result = (result)")
                }
        case 3:
                if let exsistBlock = self.blockPropertyB
                {
                    let fc = self.blockPropertyB(1,2)
                    fc("输出")
                }
        default:
                let ret = self.blockProperty(3,4)
                println(ret)
        }
    }

    //block作为函数参数
    func testBlock(blockfunc:funcBlock!)//使用!号不需要再解包
    {
        if let exsistblock = blockfunc
        {
            blockfunc() //无参无返回
        }
    }

    func testBlockA(blockfunc:funcBlockA!)
    {
        if let exsistblock = blockfunc
        {
            let retstr = blockfunc(5,6)
            println(retstr)
        }
    }

    func testBlockB(blockfunc:funcBlockB!)
    {
        if let exsistblock = blockfunc
        {
           let retfunc = blockfunc(5,6)
            retfunc("结果是")
        }
    }

    func testBlockC(blockfunc:funcBlockC!)
    {
        if let exsistblock = blockfunc
        {
            let retfunc = blockfunc(5,6)
            let str = retfunc("最终果结是")
            println(str)
        }
    }
}

执行测试码：

var bk = blockDemo()
//block设置前,啥也没有输出
bk.testProperty(0)
bk.testProperty(1)
bk.testProperty(2)
bk.testProperty(3)
println("＝＝＝＝＝＝＝＝＝＝＝＝＝＝设置block属性＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝")

bk.blockProperty = {
    (a :Int,b:Int) -> String in
    let c = a*100+b
    return "(a)*100+(b) = (c)"
}
bk.testProperty(0)

bk.blockPropertyNoReturn = {
    (param:String) -> () in
    println("input param value is : (param)")
}
bk.testProperty(1)

bk.blockPropertyA = {
    (a:Int,b:Int) -> String in
    let c = a*100+b*200
    return "(a)*100+(b)*200 = (c)"
}
bk.testProperty(2)

bk.blockPropertyB = {
    (a:Int,b:Int) -> (String)->() in
    func sumprint(result:String)
    {
        let c = a + b;
        println("sumprint func print:parame :(result) (a) + (b) = (c)")
    }

    return sumprint
}
bk.testProperty(3)
println("＝＝＝＝＝＝＝＝＝＝＝＝＝＝属性block完成＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝")

println("＝＝＝＝＝＝＝＝＝＝＝＝＝＝函数block为nil时无输出＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝")
bk.testBlock(nil)
bk.testBlockA(nil)
bk.testBlockB(nil)
bk.testBlockC(nil)
println("＝＝＝＝＝＝＝＝＝＝＝＝＝＝函数block操作＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝")
bk.testBlock({
        //do something
        println("无参无返回值block 执行")
    })

bk.testBlockA({
        (a:Int,b:Int) -> String in
        let c = a*400+b*1000
        return "(a)*400 + (b)*1000 is (c)"
    })

bk.testBlockB({
    (a:Int,b:Int) -> (String)->() in
    func sumprint(result:String)
    {
        let c = a / b;
        println("sumprint func print:parame :(result) (a) / (b) = (c)")
    }

    return sumprint
    })

bk.testBlockC({
    (a:Int,b:Int) -> (String)->String in
        func sumrsult(res:String) -> String
        {
            let c = a*a+b*a
            return "(res) (a)*(a)+(b)*(a) = (c)"
        }
        return sumrsult
    })

以上包括了block声明和使用
下面是输出结果

blockPropertyA = nil , blockPropertyB = nil
blockProperty = (Function) , blockPropertyNoReturn = (Function)

＝＝＝＝＝＝＝＝＝＝＝＝＝＝设置block属性＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
3*100+4 = 304
input param value is : OK GOOD
result = 7*100+8*200 = 2300
sumprint func print:parame :输出 1 + 2 = 3
＝＝＝＝＝＝＝＝＝＝＝＝＝＝属性block完成＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
＝＝＝＝＝＝＝＝＝＝＝＝＝＝函数block为nil时无输出＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
＝＝＝＝＝＝＝＝＝＝＝＝＝＝函数block操作＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
无参无返回值block 执行
5*400 + 6*1000 is 8000
sumprint func print:parame :结果是 5 / 6 = 0
最终果结是 5*5+6*5 = 55