Why is My Application Crashing When I Call a Method in self.parentViewController? - iphone

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.