How to preload images in a separate thread but use them in UIImageView?

Question

AFAIK, a thread can not access UI components. But I want to preload images in a background thread and then display these in an UIImageView. Do I have to use special methods to access UIImageView in the main thread then?

Answer 1

If I understood your question correctly, you're half correct. Threads can access UI components, but only the main thread can do it reliably. Your background thread can use performSelectorOnMainThread:withObject:waitUntilDone: to call up selectors in the main thread, and from those selectors interact with the UI.

Example:

[self performSelectorOnMainThread:@selector(updateImage) withObject:nil waitUntilDone:YES];