iOS detachNewThreadSelector leaking

Question

I have a UIScrollView that I am loading some images in. Sometimes I am apply an effect to an image and it takes a bit to do the pre-loading so I decided to do this on a different thread using detachNewThreadSelector. I am using the KTPhotoBrowser that is on gitHub for this.

So basically, I have a function as so.

- (void)setCurrentIndex:(NSNumber *)newIndex
{

   NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

   currentIndex_ = [newIndex integerValue];

   [self loadPhoto:currentIndex_];
   [self loadPhoto:currentIndex_ + 1];
   [self loadPhoto:currentIndex_ - 1];
   [self unloadPhoto:currentIndex_ + 2];
   [self unloadPhoto:currentIndex_ - 2];

  [self setTitleWithCurrentPhotoIndex];
  [self toggleNavButtons];
  [pool release];

}

I call this using

[NSThread detachNewThreadSelector:@selector(setCurrentIndex:) toTarget:self withObject:[NSNumber numberWithInt:5]];

When I run this, it appears to be throwing a leak. I am beginning to wonder if I should be putting the AutoRelease pool around the code in the loadPhoto method. If you are curious about this code, I have included it below.

- (void)loadPhoto:(NSInteger)index
{
   if (index < 0 || index >= photoCount_) {
      return;
   }

   id currentPhotoView = [photoViews_ objectAtIndex:index];
   if (NO == [currentPhotoView isKindOfClass:[KTPhotoView class]]) {
      // Load the photo view.
      CGRect frame = [self frameForPageAtIndex:index];
      KTPhotoView *photoView = [[KTPhotoView alloc] initWithFrame:frame];
      [photoView setScroller:self];
      [photoView setIndex:index];
      [photoView setBackgroundColor:[UIColor clearColor]];

      // Set the photo image.
      if (dataSource_) {
         if ([dataSource_ respondsToSelector:@selector(imageAtIndex:photoView:)] ==    NO) {
            UIImage *image = [dataSource_ imageAtIndex:index];
            [photoView setImage:image];
         } else {
        [dataSource_ imageAtIndex:index photoView:photoView];
         }
      }

      [scrollView_ addSubview:photoView];
      [photoViews_ replaceObjectAtIndex:index withObject:photoView];
      [photoView release];
   } else {
      // Turn off zooming.
      [currentPhotoView turnOffZoom];
   }
}

Any ideas would be greatly appreciated.

Answer 1

Your code seems ok but you are using UIKit from another thread. UIKit classes should be used only from an application’s main thread.

UIKit Framework Reference Introduction

Answer 2

Use the following

[self performSelectorInBackground:@selector(setCurrentIndex:) withObject:[NSNumber numberWithInt:5]];

instead of

[NSThread detachNewThreadSelector:@selector(setCurrentIndex:) toTarget:self withObject:[NSNumber numberWithInt:5]];

and it eliminates the memory leak.