多控制器管理

- (IBAction)back:(UIButton *)sender
{
    //通过展示控制器关闭当前窗口
    [self.presentingViewController dismissViewControllerAnimated:YES completion:nil];
   

}

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSLog(@"%@",segue.identifier);
    if ([segue.identifier isEqualToString:@"modal"])
    {
        SecondViewController *second =segue.destinationViewController;
       
        second.text = @"welcome to you";

    }

}

//定义反向传数据的代理协议
@protocol SecondViewControllerDelegate
-(void)comeback:(NSString *)str;

@end

//定义协议

@property (weak,nonatomic)id<SecondViewControllerDelegate>delegate;

//通过代理反向传数据

    [self.delegate comeback:@"Tom"];

 UIViewController<SecondViewControllerDelegate>

  second.delegate = self;

//成为消息的观察者

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(comeback:) name:SECONDVIEWCONTROLLERNOTIFICATION object:nil];

//取消观察者

[[NSNotificationCenter defaultCenter]removeObserver:self name:SECONDVIEWCONTROLLERNOTIFICATION object:nil];

//通过通知方式反向传数据

[[NSNotificationCenter defaultCenter]postNotificationName:SECONDVIEWCONTROLLERNOTIFICATION object:nil userInfo:@{SECONDVIEWCONTROLLERNOTIFICATIONKey:@"Tom"}];

//从通知对象取出数据

NSDictionary *data = notification.userInfo;

self.Label.text = [data objectForKey:SECONDVIEWCONTROLLERNOTIFICATIONKey];