刚刚进入ios开发行业，发现开发中要用到大量的block回调，由此可见它的重要性。学习它之前我也是网上找的资料，推荐这篇文章http://blog.csdn.net/mobanchengshuang/article/details/11751671，我也是从这里得到一点启示。假设对block的使用还不熟悉建议先看我的block那篇文章。以下我用自己的project来解释一下block回调函数。

一、先创建一个简单的xcodeproject

ViewController.h文件

//

//  ViewController.h

//  block回调

//

//  Created by pengxun523 on 14-4-16.

//  Copyright (c) 2014年 pengxun523. All rights reserved.

//

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UIButton *btnOutlet;

- (IBAction)btnClick:(UIButton *)sender;

@end

#import "ViewController.h"

#import "ShowBtnColor.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad

{

[super viewDidLoad];

}

-(void)chargeMyIphone:(void(^)(void))finishBlock

{

}

- (void)didReceiveMemoryWarning

{

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

- (IBAction)btnClick:(UIButton *)sender

{

CGRect temp = CGRectMake(_btnOutlet.frame.origin.x, _btnOutlet.frame.origin.y, _btnOutlet.frame.size.width+50, _btnOutlet.frame.size.height+20);

[ShowBtnColor ChangeRootViewBtnRect:temp blockcompletion:^(UIColor *colorEnum) {

/*函数回调 当block运行时就会回到这里*/

_btnOutlet.backgroundColor = colorEnum;

}];

}

@end

ShowBtnColor.h文件

//

//  ShowBtnColor.h

//  block回调

//

//  Created by pengxun523 on 14-4-22.

//  Copyright (c) 2014年 pengxun523. All rights reserved.

//

#import <Foundation/Foundation.h>

typedef void (^Changcolor)(UIColor *colorEnum); //定义一个block返回值void參数为颜色值

@interface ShowBtnColor : NSObject

//回调函数改变btn的颜色值

+ (void)ChangeRootViewBtnRect:(CGRect)rect blockcompletion:(Changcolor)Changcolorblock;

@end

 当点击button时