在解除ModalViewController后刷新父ViewController

Question

在我的iOS应用程序中,用户可以从列表中选择一个图像,在该图像上显示一个包含图像的模态和删除图像的选项.如果用户选择删除图像,则返回到包含图像列表的原始viewController.我需要刷新原始ViewController以考虑已删除的图像.

当图像被删除到父视图控制器时,我尝试使用NSNotificationCenter进行广播.但是,似乎从未收到广播.

还有其他方法吗？

1. 在解除模态后将数据发送回父ViewController,并且
2. 检测何时从父ViewController中解除模态？

(我试着按照这里列出的例子,但它似乎没有工作)

以下是我的代码:

EditStepViewController(原始视图控制器):

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
MediaPreviewViewController *mediaPreviewVC = (MediaPreviewViewController *)[storyboard instantiateViewControllerWithIdentifier:@"MediaPreviewViewController"];
mediaPreviewVC.selectedImageURL = [NSString stringWithFormat:@"%@",gestureRecognizer.view.tag];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:mediaPreviewVC];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(didDismissMediaPreview)
                                             name:@"MediaPreviewDismissed"
                                           object:nil];
[self presentViewController:navigationController animated:YES completion:nil];

MediaPreviewViewController(第二个ViewController):

 ...
 [self deleteImage];
 [[NSNotificationCenter defaultCenter] postNotificationName:@"MediaPreviewDismissed" object:nil userInfo:nil];
 [self dismissViewControllerAnimated:YES completion:^(){
   NSLog(@"dismissed controller");
  }];

然后,回到EditStepViewController:

-(void)didDismissMediaPreview{
    NSLog(@"dismissed media preview"); // this is never logged!
    [self.view setNeedsDisplay]; // refresh view to account for deleted image
}

在此先感谢您的帮助!

Answer 1

在我的情况下,我通常在这里使用块.

例如,您有ParentViewController.h

@interface ParentViewController : UIViewController
@end

实现ParentViewController.m

// INCLUDE HERE THE MODAL CONTROLLER TO HAVE ACCESS TO ITS PUBLIC PROPERTY
#import ModalViewController.h

@implementation ParentViewController

// implement your modal dismiss block here
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
   // DEFINE HERE THE CALLBACK FUNCTION
   // 1. get the model view controller
   ModalViewController *mvc = [segue destinationViewController];

   // 2. Your code after the modal view dismisses
   mvc.onDismiss = ^(UIViewController *sender, NSObject *objectFromModalViewController)
   {
       // Do your stuff after dismissing the modal view controller
       .
       .
       .
   }
} 
@end

而且,ModalViewController.h

@interface ModalViewController : UIViewController

// call back function, a block
@property (nonatomic, strong) void (^onDismiss)(UIViewController *sender, NSObject *objectYouWantToPassBackToParentController)
@end

ModalViewController.m

@implementation ModalViewController

.
.
.

// your dismiss function say
- (IBAction)dismissViewController:(id)sender
{
   ... 

   [self deleteImage];

   [self dismissViewControllerAnimated:YES completion:^
   {
      // MAKE THIS CALL
      self.onDismiss(self, theOjectYouWantToPassBackToParentVC);
   }];
}
@end