message sent to deallocated instance issue - iphone

Question

I have been debugging the following issue for the past couple hours and can't seem to come up with a good conclusion.
-[NSIndexPath row]: message sent to deallocated instance 0x506cf90
I am implementing a swipe recognizer on each cell on the UITableView. Whenever a swipe is detected, the code below will be called. What it does is to show/hide a subview in the cell. If the subview already shows then it hides, otherwise it shows. If a subview is already shown on cell 5 and a swipe is detected on cell 3 then we remove that subview first then add the subview on cell 3.
I tried the code below and it seems to works with some cells. However, there is a cell particularly at the bottom of the UITableView in which if I try to hide the subview it gives me the error above. It works just perfectly fine for the other cell, just cells at the bottom. Why is this?
The code is as follows:
- (void)swipe:(UISwipeGestureRecognizer *)recognizer direction:(UISwipeGestureRecognizerDirection)direction
{
if (recognizer && recognizer.state == UIGestureRecognizerStateEnded)
{
// Get the table view cell where the swipe occured
CGPoint location = [recognizer locationInView:self.table];
NSIndexPath* indexPath = [self.table indexPathForRowAtPoint:location];
ConvoreCell* cell = (ConvoreCell *) [self.table cellForRowAtIndexPath:indexPath];
[self.table beginUpdates];
NSLog(#"ROW is %d", global.row);
//removing the options view at the other cell before adding a new one
if (global != nil && global.row != indexPath.row){
[sideSwipeView removeFromSuperview];
[sideSwipeView release];
sideSwipeView = nil;
}
//options already exist, we need to remove it
if (sideSwipeView != nil){
[sideSwipeView removeFromSuperview];
[sideSwipeView release];
sideSwipeView = nil;
slide = NO;
} else {
//options do not exist and therefore we need to add it
NSArray * buttonData = [[NSArray arrayWithObjects:
[NSDictionary dictionaryWithObjectsAndKeys:#"Mark Read", #"title", #"mark.png", #"image", nil],
[NSDictionary dictionaryWithObjectsAndKeys:#"Track", #"title", #"play.png", #"image", nil],
[NSDictionary dictionaryWithObjectsAndKeys:#"Leave", #"title", #"delete.png", #"image", nil],
nil] retain];
NSMutableArray * buttons = [[NSMutableArray alloc] initWithCapacity:buttonData.count];
sideSwipeView = [[UIView alloc] initWithFrame:CGRectMake(0, cell.frame.size.height-25, 320, 25)];
[sideSwipeView setAutoresizingMask:UIViewAutoresizingFlexibleTopMargin];
[sideSwipeView setBackgroundColor:[UIColor colorWithPatternImage: [UIImage imageNamed:#"dotted-pattern.png"]]];
[sideSwipeView setTag:-10];
CGFloat leftEdge = BUTTON_LEFT_MARGIN;
for (NSDictionary* buttonInfo in buttonData)
{
if (!([[buttonInfo objectForKey:#"title"] isEqualToString:#"Mark Read"] && [[[groups objectAtIndex:indexPath.row] unread] intValue] == 0))
{
UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom];
button.autoresizingMask = UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleTopMargin;
UIImage* buttonImage = [UIImage imageNamed:[buttonInfo objectForKey:#"image"]];
if ([[[groups objectAtIndex:indexPath.row] tracked] intValue] == 1 && [[buttonInfo objectForKey:#"title"] isEqualToString:#"Track"]){
buttonImage = [UIImage imageNamed:#"pause.png"];
[button setSelected:YES];
} else
[button setSelected:NO];
button.frame = CGRectMake(leftEdge, 0, buttonImage.size.width, buttonImage.size.height);
UIImage* grayImage = [self imageFilledWith:[UIColor colorWithWhite:0.9 alpha:1.0] using:buttonImage];
[button setImage:grayImage forState:UIControlStateNormal];
if ([[buttonInfo objectForKey:#"title"] isEqualToString:#"Mark Read"]){
[button addTarget:self action:#selector(markRead:) forControlEvents:UIControlEventTouchUpInside];
} else if ([[buttonInfo objectForKey:#"title"] isEqualToString:#"Track"]){
[button addTarget:self action:#selector(track:) forControlEvents:UIControlEventTouchUpInside];
} else if ([[buttonInfo objectForKey:#"title"] isEqualToString:#"Leave"]){
[button addTarget:self action:#selector(leave:) forControlEvents:UIControlEventTouchUpInside];
}
[button setTag:indexPath.row];
[buttons addObject:button];
[sideSwipeView addSubview:button];
leftEdge = leftEdge + buttonImage.size.width + BUTTON_SPACING;
}
}
[cell.contentView addSubview:sideSwipeView];
[buttons release];
[buttonData release];
global = indexPath;
slide = YES;
}
[self.table endUpdates];
[self.table deselectRowAtIndexPath:indexPath animated:YES];
}
}
Now the issue here is that the pointer to indexPath somehow got deallocated. I was able to get around this by making a copy of the indexPath instead of just having a reference to the pointer. So I did:
global = [indexPath copy];
for some reason after this method is called it deallocates indexPath and I am not sure who does it.. I think iOS does it... is it true?

Answer 1

NSIndexPath* indexPath = [self.table indexPathForRowAtPoint:location];
That returns an autoreleased instance. So, yes, your assignment to global needs to retain the object. copy effectively returns a retained instance.
Don't leak, though. If you just do:
global = [indexPath copy];
And you don't release the original value of global first, you'll leak.
Oh, and: http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html