初探swift语言的学习笔记十(block)

作者：fengsh998

原文地址：http://blog.csdn.net/fengsh998/article/details/35783341

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在前面一些学习中，原本把闭包给理解成了block尽管有很多相似之处，但block还是有他自己的独特之外。近日，在写oc/swift混合编码时，有时候需要swift回调oc,oc回调swift 。

因此我把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。废话不说多，上例子：

//
//  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

好了，我想这个比文字语方描述的更为清楚吧。如有不明白或其它奇怪写法，欢迎踢馆。。。。。