block回调

• 情景：viewController2给viewController1传值，将viewController1的按钮名字改为“已点击”

• viewController2.h代码

import <UIKit/UIKit.h>

typedef void(^Myblock)(NSString *);
@interface ViewController2 : UIViewController
@property(nonatomic,copy) Myblock firstBlock;
@end

- viewController2.m代码

• (void)viewDidLoad {
  [super viewDidLoad];
  self.firstBlock(@"已点击");
  }

- viewController1.h代码

• (void)viewDidLoad {
  [super viewDidLoad];
  [self.btn setTitle:@"跳转" forState:UIControlStateNormal];

-  viewController1.m代码

• (IBAction)click:(UIButton )sender {
  ViewController2two = [[ViewController2 alloc]init];
  two.frstBlock = ^(NSString * name) {
  [_btn setTitle:name forState:UIControlStateNormal];
  NSLog(@"peibobo---%@",name);
  };
  [self presentViewController:two animated:YES completion:nil];
  }