Xcode Unrecognized Selector Error

Question

I've been having a ton of issues with this section of an app that I'm writing, I'm sure people here are getting sick of me so I'm going to try and solve all my questions in this post. I'm working on an app that behaves like a photo gallery, and I'm implementing the option to have the user delete photos from their gallery. To accomplish this, I decided to place an invisible button over each picture. When the user hits an "Edit" button, the hidden delete buttons over each picture become active. I'm using the same IBOutlet over each of the hidden buttons for simplicity, and I've tagged each button appropriately in Interface Builder. When the user taps the button over the picture, an alert view appears asking if they really want to delete it. If they click yes, I call removeObjectAtIndex and delete the image from the UI. But, when I click "Yes" in the alert view, I get an error from Xcode stating:

2012-04-04 11:26:40.484 AppName[608:f803] -[UIButton setImage:]: unrecognized selector sent to instance 0x6a922c0

2012-04-04 11:26:40.485 AppName[608:f803] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIButton setImage:]: unrecognized selector sent to instance 0x6a922c0'*

I've been trying to figure out what is causing this for a few hours now to no avail. I'm not setting the image of a UIButton anywhere in my code. I did in IB, but I simply set the buttons types to Custom so that they appear invisible. I will post my entire file below, I can't find any issues in my code, so any help is much appreciated! Thanks. EDIT Here is the current version of the code:

    - (IBAction)grabImage {
    self.imgPicker = [[UIImagePickerController alloc] init];
    self.imgPicker.delegate = self;
    self.imgPicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
        _popover = [[UIPopoverController alloc] initWithContentViewController:imgPicker];
        [_popover presentPopoverFromRect:self.imageView.bounds inView:self.imageView permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
    } 

    else {
        [self presentModalViewController:imgPicker animated:YES];
    }
    [self.imgPicker resignFirstResponder];
}
// Sets the image in the UIImageView
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {
    if (imageView.image == nil) {
        imageView.image = img;

        self.array = [NSMutableArray arrayWithObject:[NSData dataWithData:UIImagePNGRepresentation(imageView.image)]];

        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;

    }

    if (imageView2.image == nil) {
        imageView2.image = img;
        NSLog(@"The image is a %@", imageView);
        [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView2.image)]];

        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;
    }

    if (imageView3.image == nil) {
        imageView3.image = img;

        [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView3.image)]];

        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;
    }

    if (imageView4.image == nil) {
        imageView4.image = img;

        [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView4.image)]];

        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;
}
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        self.title = NSLocalizedString(@"Photo Gallery", @"Photo Gallery");
        self.tabBarItem.image = [UIImage imageNamed:@"42-photos.png"];
    }
    return self;
}
////start of saving////


- (void)applicationDidEnterBackground:(UIApplication*)application {
    NSLog(@"Image on didenterbackground: %@", imageView);
    self.array = [NSMutableArray arrayWithObject:[NSData dataWithData:UIImagePNGRepresentation(imageView.image)]];

    [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView2.image)]];
     [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView3.image)]];
      [self.array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView4.image)]];

            [self.user setObject:self.array forKey:@"images"];
    [user synchronize];

            }

- (void)viewDidLoad
    {
        self.user = [NSUserDefaults standardUserDefaults];
        NSLog(@"It is %@", self.user);
        self.array = [[self.user objectForKey:@"images"]mutableCopy];
        imageView.image = [[UIImage alloc] initWithData:[self.array objectAtIndex:0]];
        imageView2.image = [[UIImage alloc] initWithData:[self.array objectAtIndex:1]];
        imageView3.image = [[UIImage alloc] initWithData:[self.array objectAtIndex:2]];
        imageView4.image = [[UIImage alloc] initWithData:[self.array objectAtIndex:3]];



        UIApplication *app = [UIApplication sharedApplication];
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationDidEnterBackground:)
                                                     name:UIApplicationDidEnterBackgroundNotification
                                                   object:app];

        backToGalleryButton.hidden = YES;
        tapToDeleteLabel.hidden = YES;
        deleteButton1.hidden = YES;
        [super viewDidLoad];

    }




///// shows the hidden and invisible "delete" button over each photo.
- (IBAction)editButtonPressed:(id)sender {
    grabButton.hidden = YES;
    editButton.hidden = YES;
    backToGalleryButton.hidden = NO;
    tapToDeleteLabel.hidden = NO;
    deleteButton1.hidden = NO;
}
////

// This is when the user taps on the image to delete it.
- (IBAction)deleteButtonPressed:(id)sender {
    NSLog(@"Sender is %@", sender);
    UIAlertView *deleteAlertView = [[UIAlertView alloc] initWithTitle:@"Delete"
                                                              message:@"Are you sure you want to delete this photo?"
                                                             delegate:self
                                                    cancelButtonTitle:@"No"
                                                    otherButtonTitles:@"Yes", nil];
    [deleteAlertView show];
    int imageIndex = ((UIButton *)sender).tag;
    deleteAlertView.tag = imageIndex;

}

- (void)alertView: (UIAlertView *) alertView 
clickedButtonAtIndex: (NSInteger) buttonIndex
{


    if (buttonIndex != [alertView cancelButtonIndex]) {
        NSLog(@"User Clicked Yes. Deleting index %d of %d", alertView.tag, [array count]);
        NSLog(@"The tag is %i", alertView.tag);
        [self.array removeObjectAtIndex: alertView.tag];
        NSLog(@"After deleting item, array count  = %d", [array count]);
    NSLog(@"Returned view is :%@, in view: %@", [self.view viewWithTag:alertView.tag], self.view);
        ((UIImageView *)[self.view viewWithTag:alertView.tag]).image =nil;
    }

    [self.user setObject:self.array forKey:@"images"];
}

Update: I added breakpoints, and discovered that ((UIImageView *)[self.view viewWithTag:alertView.tag]).image =nil; is the line that is causing the crash, I still can't figure out why though.

Answer 1

I don't see setImage: being called in any of that code you pasted into your question, but I can tell you this: UIButton's setImage method actually requires a button state as a second parameter.

e.g.

[UIButton setImage: forState:]

I've linked Apple's documentation for you.

If your calls to setImage: don't have a second parameter, that would explain the "unrecognized selector error" you're seeing.

Answer 2

This is an extension to @MichaelDautermann , who makes a very good point that a UIButton has a setImage:forState: method, but no setImage method. However, you ARE calling set image. Not on a button, but when you say imageView.image and imageView2.image. This invokes the setter method for the image view. I would set a breakpoint (or use NSLog and the %@ item) to ensure that imageView is in fact an imageView and not a button. If it somehow changed from under you, this could be causing the issue. Simply set a break point at those two lines and see if you even make it past them.

Additionally, if Xcode isn't popping you over to which line is actually causing the issue, check your crash logs. Symbolicated, the log will give you the line number. Or, a less direct approach would be to set breakpoints at the ends of the methods you provided in your answer, and see how many you get past. Once you crash, you can narrow down which method is causing you grief, and then start setting break points within the method until you get to the line in question.

UPDATE: You said in the comments that ((UIImageView *)[self.view viewWithTag:alertView.tag]).image =nil is what you have, but self.view is a UIControl. Changing the cast won't affect the result. Is the UIImageView whose image you are trying to delete a subview of a UIControl? If not, you're never going to get the image view back from viewWithTag. Generally, self.view refers to a view controller's view, so if you're getting a UIControl, my assumption is either your whole view is a UIControl, or you're doing this in the wrong class. Which class are you doing this in, and what is it a subclass of? It appears you are doing this in a view controller, but I just want to be sure. And again, in either case (UIControl or UIImageView), neither class responds to setImage.