Block回调

    void (^YzmBlockHuiDiao)(NSString*value);

    YzmBlockHuiDiao=^(NSString*name)

    {

        [BTN setTitle:name forState:UIControlStateNormal];

    };

    YzmBlockHuiDiao(@"我是鱼儿fei");

一般block用的回调多所以稍微改动下，假设A界面跳往B界面，然后回调

、、、、、、、、、、这个是A界面的.M文件

- (void)viewDidLoad

{

    [superviewDidLoad];

    self.view.backgroundColor=[UIColorwhiteColor];

    self.title=@"A界面";

    BTN=[[UIButtonalloc]initWithFrame:CGRectMake(0,140, self.view.frame.size.width,60)];

    BTN.backgroundColor=[UIColorredColor];

    [BTNsetTitle:@"按钮"forState:UIControlStateNormal];

    [BTNaddTarget:selfaction:@selector(toNextVC)forControlEvents:UIControlEventTouchUpInside];

    [self.viewaddSubview:BTN];

    

}

-(void)toNextVC

{

    BViewController*BVC=[[BViewControlleralloc]init];

    BVC.block=^(NSString*name)

    {

        [BTNsetTitle:name forState:UIControlStateNormal];

    };

    [self.navigationControllerpushViewController:BVC animated:YES];

}

、、、、、、、、、、这个是B界面的文件

#import <UIKit/UIKit.h>

typedef void (^YzmBlockHuiDiao)(NSString*value);

@interface BViewController : UIViewController

@property(nonatomic,copy)YzmBlockHuiDiao block;

@end

- (void)viewDidLoad

{

    [superviewDidLoad];

    self.view.backgroundColor=[UIColorwhiteColor];

    self.title=@"B界面";

    self.block(@"我是鱼儿fei");

}