Question

So I have an iOS5 application (xcode 4.2) where I have a viewcontroller with a UIImageView set to a certain image. I would like to change this image to another image after 2 seconds. There is no user interaction, and the only thing that needs to happen is for the image to change after 2 seconds. I found information on dispatch_time, so I tried that.

If you type dispatch_time in main.m, it gives you a few lines of code and you need to insert what it should do after 2 seconds. My questions:

1. Is the dispatch_time code indeed meant to go in main.m ? Assume that this application does nothing else than change the UIImageView to display another image after 2 seconds.

2. How do I reference the UIImageView from main.m? The declaration in the view controller .h file is like this:

   @property (weak, noatomic) IBOutlet UIImageView *Image;

Answer 1

Use the dispatch code in your view controller, probably in viewDidLoad:

- (void)viewDidLoad {
    ...

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2.0 * NSEC_PER_SEC), dispatch_get_current_queue(), ^{
        self.Image.image = [UIImage imageNamed:@"anotherImage.png"];
    });
}