Question

I’m making an app that is kinda like iBooks. There is some stuff on the screen, each item represented by a small thumbnail. I want the user to be able to delete the items much like when you tap the “Edit” button in iBooks – an X comes up, and the item is deleted. I’m using the delegation pattern to handle all of this, so here is some code:

// Button is created in CustomView.h class
UIImage *deleteImage = [UIImage imageNamed:@"delete.png"];
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
self.deleteButton = button;
[self.deleteButton setImage:deleteImage forState:UIControlStateNormal]; 
[self.deleteButton addTarget:self action:@selector(deleteIt) forControlEvents:UIControlEventTouchUpInside];

// Here's what's called when the delete button is pushed
- (IBAction)deleteMap {
[self.customViewDelegate itemWasDeleted:self];  
}

// And here's the implementation of that method, in a View Controller
- (void)itemWasDeleted:self:(CustomView*)customView {
    // delete domain object
    // . . .    

    [self.collectionOfCustomViews removeObject:customView];
    [customView removeFromSuperview];
}

The problem with this code is that I get a Bad Access Exception. Via NSZombie, looks like this:

* -[UIButton _unhighlight]: message sent to deallocated instance 0x5f4a740

I guess what’s happening is that when my target-action implementation is called, it’s not yet safe to release the button, as I’m doing in my delegate method. So my question is, what’s a better approach to doing this so that may app doesn’t crash? I’d like to know the cleanest approach possible.

Answer 1

If collectionOfCustomViews was the only object retaining customView then you released it when you removed it, so it can’t respond to removeFromSuperview.