关于OC中的block自己的一些理解（二）

一、block延伸：页面间反向传值

1）first页面的代码

- (void)viewDidLoad {[super viewDidLoad];[self setupBtn];self.view.backgroundColor = [UIColor whiteColor];}
- (void)setupBtn
{UIButton * btn = [[UIButton alloc]init];[btn addTarget:self action:@selector(buttonClick) forControlEvents:UIControlEventTouchUpInside];btn.backgroundColor = [UIColor blackColor];btn.frame = CGRectMake(100, 100, 100, 100);[self.view addSubview:btn];
}
- (void)buttonClick
{SecondViewController * secondVC = [[SecondViewController alloc]init];//在first页面调用block输出字符串secondVC.myBlock= ^(NSString * str){NSLog(@"%@",str);};[self.navigationController pushViewController:secondVC animated:YES];
}

2）second页面的代码

//.h文件
#import <UIKit/UIKit.h>@interface SecondViewController : UIViewController
//定义block
@property (nonatomic,copy)void (^myBlock)(NSString * str);
@end
//.m文件
- (void)setupBtn
{UIButton * btn = [[UIButton alloc]init];[btn addTarget:self action:@selector(buttonClick) forControlEvents:UIControlEventTouchUpInside];btn.backgroundColor = [UIColor blackColor];btn.frame = CGRectMake(100, 100, 100, 100);[self.view addSubview:btn];
}
- (void)buttonClick
{//通过block传值if (self.myBlock) {self.myBlock(@"haha");}[self.navigationController popToRootViewControllerAnimated:YES];
}

输出结果：

2016-02-19 11:36:55.168 03-block[983:70116] haha

参考博客：http://my.oschina.net/leejan97/blog/268536?fromerr=2UdIND3G