GDC dispatch example

gistfile1.m

-(void)viewDidLayoutSubviews
{   [super viewDidLayoutSubviews];
    dispatch_queue_t imageReader = dispatch_queue_create("Image Reader", NULL);
    dispatch_async(imageReader, ^{
        [NSThread sleepForTimeInterval:1];
      UIImage *image = [UIImage imageNamed:self.imageName]; // may take time to load
        dispatch_async(dispatch_get_main_queue(), ^{
        self.imageView.image = image;
        self.imageView.contentMode = UIViewContentModeTopLeft;
        self.imageView.contentMode = UIViewContentModeTopLeft;
        self.scrollView.contentSize = self.imageView.image.size;
        self.imageView.frame = CGRectMake(0, 0, self.imageView.image.size.width, self.imageView.image.size.height);
        });
    });
    
}