UIImageView showing the image only after changing tabs in the UITabBarViewController

[tresnotas]

I have a UIScrollViewController that has a UIScrollView which holds an UIImageView inside. In loadView of the the scroll view controller I download the image by calling a function, that's supposed to do the downloading on a different thread. I call this function from my loadView and then put the imageview inside the scrollview, and set the scrollview as the view of the controller.

The problem is I can't see the image when I run the program, after clicking a row in the tableView (which is supposed to push the scrollview with the image in it). However, if I change tabss (in the tabbarviewcontroller) and come back to this tab. The image will show.

So I think the image download happens, but I somehow have a problem showing it instantly on the screen. It only appears after I come back to it. What do I seem to be doing wrong? I'm new to threads so I suspect it's a problem with that. Also my code was working before I made it so that it would do the download in another thread, so I'm pretty sure it is related to that.

This is the function in the Photo.m which is an Entity in Core Data. This is supposed to do the download

- (void)processImageDataWithBlock:(void (^)(NSData *imageData))processImage { 
    NSString *url = self.imageURL;
dispatch_queue_t callerQueue = dispatch_get_current_queue();   
dispatch_queue_t downloadQueue = dispatch_queue_create("Flickr download", NULL); 
dispatch_async(downloadQueue, ^{
    NSData *imageData = [FlickrFetcher imageDataForPhotoWithURLString:url];

    dispatch_async(callerQueue, ^{

        processImage(imageData);   

    });

});
}

This is my loadView method in the PhotoScrollViewController.m

- (void)loadView {

    [image processImageDataWithBlock:^(NSData *imageData) {

        UIImage *imageToBeShown = [UIImage imageWithData:imageData];        


        imageView = [[UIImageView alloc] initWithImage:imageToBeShown];
        CGRect applicationFrame = [[UIScreen mainScreen] applicationFrame];
        scrollView = [[UIScrollView alloc] initWithFrame:applicationFrame];
        scrollView.delegate = self;
        scrollView.contentSize = imageToBeShown.size;

        [scrollView addSubview:imageView];
        self.title = image.title;
        self.view = scrollView;
    }];
      }