Question

In my code I’m doing the following:

-(void)pushCropImageViewControllerWithDictionary:(NSDictionary *)dictionary {
civc = [[CropImageViewController alloc] init];
[self presentModalViewController:civc animated:YES];
civc.myImage.image = [dictionary objectForKey:UIImagePickerControllerOriginalImage];

}

So I have a modal view in my app. When this modal view dismisses, I want to call a method from the parent view (the view that called pushCropImageViewControllerWithDictionary), like this:

-(void)viewWillDisappear:(BOOL)animated {
[super viewWillAppear:animated];
[(AddNewItemViewController *)self.parentViewController addCroppedPicture:screenshot];

}

But it keeps crashing with the following message:

Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘-[UITabBarController addCroppedPicture:]: unrecognized selector sent to instance 0x4d15930’

Can someone tell me what am I doing wrong? I am including the header for AddNewItemViewController so the selector should be recognized. Can someone give me a hand on how can I do this properly? Thanks.

EDIT: Declaration of addCroppedPicture:

-(void)addCroppedPicture:(UIImage *)image;

The implementation itself is empty so far.

Answer 1

Apparently, self.parentViewController isn’t an instance of AddNewItemViewController but the tab bar controller. Hence the crash.

The proper solution is to make a delegate:

-(void)pushCropImageViewControllerWithDictionary:(NSDictionary *)dictionary
{
    civc = [[CropImageViewController alloc] init];
    civc.delegate = self;
    [self presentModalViewController:civc animated:YES];
    ...
}

To send a message back to the delegate:

-(void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [self.delegate addCroppedPicture:screenshot];
}

It’s up to you do declare the delegate protocol:

@protocol CropImageDelegate <NSObject>
- (void)addCroppedPicture:(UIImage*)image;
@end

And add a property for the delegate to CropImageViewController:

@property (nonatomic, assign) id<CropImageDelegate> delegate;

And finally, make your view controller conform to this delegate protocol.