作者：fengsh998原文地址：http://blog.csdn.net/fengsh998/article/details/35783341转载请注明出处如果觉得文章对你有所帮助，请通过留言或关注微信公众帐号fengsh998来支持我，谢谢！
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 = nilblockProperty = (Function) , blockPropertyNoReturn = (Function)＝＝＝＝＝＝＝＝＝＝＝＝＝＝设置block属性＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝3*100+4 = 304input param value is : OK GOODresult = 7*100+8*200 = 2300sumprint 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 8000sumprint 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。。。。。