其实，iOS中的Block就是C++中的函数指针，实现方式都是一样的，下面贴出一个简单的实践。

首先，创建一个回调的类

BlockStudy.h

//
//  BlockStudy.h
//  BlockStudy
//
//  Created by 杜甲 on 11/11/14.
//  Copyright (c) 2014 杜甲. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface BlockStudy : NSObject

typedef void (^TestBlock)();
@property (nonatomic , strong) TestBlock testBlock;


- (void)StartBlock;
@end

//
//  BlockStudy.m
//  BlockStudy
//
//  Created by 杜甲 on 11/11/14.
//  Copyright (c) 2014 杜甲. All rights reserved.
//

#import "BlockStudy.h"

@implementation BlockStudy

- (void)test
{
    if (_testBlock) {
        _testBlock();
    }
}

- (void)StartBlock
{
    [self performSelector:@selector(test) withObject:nil afterDelay:2.0];
}

@end

调用类ViewController.m

//
//  ViewController.m
//  BlockStudy
//
//  Created by 杜甲 on 11/11/14.
//  Copyright (c) 2014 杜甲. All rights reserved.
//

#import "ViewController.h"
#import "BlockStudy.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    BlockStudy *block = [[BlockStudy alloc] init];
    block.testBlock = ^()
    {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Block学习" message:@"测试成功" delegate:self cancelButtonTitle:@"取消吧" otherButtonTitles:@"OK", nil];
        [alert show];
        
    };
    [block StartBlock];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

iOS 使用Block实现函数回调