一、Block的基本概念
Block是程序的代码块,这个代码块可以在需要的时候执行。IOS开发中,block到处可见,所以学好很重要
二、Block的基本用法
//
// main.m//
Block//
// Created by Joe on 15-2-23.//
Copyright (c) 2015年 apple. All rights reserved.//#import <Foundation/Foundation.h>//最基本的用法
void test(){
{
int (^Sum)(int,
int) = ^(int a,
int b) {
{
return a + b; }; NSLog(
};
NSLog(@"%d",
Sum(10,
11));}}//也是基本用法,另外Block代码段中可以使用外边的mul变量,但是不可以改变他的值,如果下改变他的值,可以使用__block来定义mul
void test1(){
{
int mul =
7;
int (^myBlock)(int) = ^(int
num) {
{
return mul * num; };
};
int c = myBlock(7);
NSLog(
NSLog(@"%d",
c);}}//改变外边变量的值
void test2(){ __block
{
__block int mul =
7;
int (^myBlock)(int) = ^(int
num) { mul
{
mul =
10; NSLog(
NSLog(@"mul is %i",
mul);
return mul * num; };
};
int c = myBlock(7);
NSLog(
NSLog(@"%d",
c);}}//给block起一个别名,之后我们就可以任意命名的来使用block
void test3(){ typedef
{
typedef int (^MySum)(int,
int); MySum sum
MySum sum = ^(int a,
int b) {
{
return a + b; };
};
int c = sum(20,
39); NSLog(
NSLog(@"%d",
c); }
}int main(int
argc,
const
char * argv[]){ @autoreleasepool { test(); }
{ @autoreleasepool {
test();
}
return
0;}
}
OK,都有注释。在main函数中调用即可测试
三、Block来实现委托模式
//
// Button.h//
Block_Button//
// Created by JOe on 15-3-23.//
Copyright (c) 2015年 apple. All rights reserved.//#import <Foundation/Foundation.h>
@class Button;//给block给一个别名ButtonBlock
typedef
void (^ButtonBlock)(Button *);@interface
Button : NSObject//定义一个block的成员变量,暂时写成assign
@property (nonatomic, assign) ButtonBlock block;-(void)click;@end
//
// Button.m//
Block_Button//
// Created by JOe on 15-3-23.
// Copyright (c) 2015年 apple. All rights reserved.
//#import "Button.h"@implementation Button//模拟点击-(void)click{
{
//回调函数,回调block
_block(self);
}@end
//
// main.m// Block_Button//
//
// Created by JOe on 15-3-23.
// Copyright (c) 2015年 apple. All rights reserved.
//#import <Foundation/Foundation.h>#import "Button.h"int main(int argc, const char * argv[]){ @autoreleasepool { Button
{ @autoreleasepool {
Button *btn = [[[Button alloc] init] autorelease];
//回调的函数
btn.block = ^(Button *btn) { NSLog(
{
NSLog(@"%@被点击", btn); }; [btn click]; }
};
[btn click];
}
return 0;}
}