Question

I’m nearing the end of a school project with programming in Xcode, but right now I’m having a small yet extremely annoying issue: a memory leak. The leak has been traced down to the following line of code:

@autoreleasepool {
    [NSThread detachNewThreadSelector:@selector(updateThread) toTarget:self withObject:nil];
}

When I comment this out, the leak is gone. Apparently something goes wrong in the autoreleasepool: I’m still a bit new on these (especially when using ARC), but threads like this one made it clear to me that using @autoreleasepool should be sufficient.

For some reason, this is not the case for my code. I guess I’m missing something here: if someone could give some ideas on what the issue could be, then that would be highly appreciated. Just tell me if I have to post more code, that won’t be a problem: it’s just for the readability of the question that I try to limit it to the main issue.

Thanks in advance!

EDIT:

Thank you for the first responses! The issue still persists however… I will post a bit more code to clear things up a bit. The thread is started in viewDidLoad:

/*
 Everything mentioned here will be done after loading.
 */
- (void)viewDidLoad
{
    // Do standard setup
    [super viewDidLoad];

    // Do any additional setup before loading the view from its nib.
    self.title = @"Blog Manager";

    // Activate edit mode
    [tbvBlogList setEditing:YES animated:YES];
    tbvBlogList.allowsSelectionDuringEditing = YES;

    [NSThread detachNewThreadSelector:@selector(updateThread) toTarget:self withObject:nil];

    UIImage *btnImage = [UIImage imageNamed:@"iPhone_General_Button_Add_Blog.png"];
    UIButton *viewBtnAddBlog = [UIButton buttonWithType:UIButtonTypeCustom];
    [viewBtnAddBlog setImage:btnImage forState:UIControlStateNormal];
    viewBtnAddBlog.frame = CGRectMake(0, 0, 80, 36);
    [viewBtnAddBlog addTarget:self action:@selector(addBlogByButton:) forControlEvents:UIControlEventTouchUpInside];

    UIBarButtonItem *btnAddBlog = [[UIBarButtonItem alloc] initWithCustomView:viewBtnAddBlog];
    btnAddBlog.tintColor = [UIColor clearColor];
    self.navigationItem.rightBarButtonItem = btnAddBlog;
}

Then, the other functions that are used for the threading:

/*
 Thread to update the progress bar with.
 */
- (void)updateThread
{
    @autoreleasepool {
        while(YES){
            [self performSelectorOnMainThread:@selector(updateProgressBar) withObject:nil waitUntilDone:false];
            [NSThread sleepForTimeInterval:0.1f];
        }
    }
}

/*
 Updates the progress bar.
 */
- (void)updateProgressBar
{
    pvProgress.progress = dProgress;
}

If it is anything worth mentioning: I’m using Xcode 4.2.1. Thanks again for the support!

Answer 1

Right now I just want to hit myself with a rock.

I just realized the “while”-loop never stops. Of course this means the thread will keep running, therefore the memory won’t ever be released until the app finishes.

By simply adding a boolean that is set to “NO” when the thread should quit, the issue was solved. Everyone: thanks you very much for looking at this problem for me. Sometimes the biggest problems have the smallest solutions…