You can find all sorts of interesting and useful stuff in Apple’s header files. Don’t be afraid to explore them. I usually troll through the headers when a new major SDK version comes out (like IOS 7 probably will be this year) to see what’s new. I also use them for API exploration. As always, when in doubt be sure to read the official documentation. Apple’s documentation is good. It’s also voluminous. But once you’ve marinated in a framework for awhile, you know how things work and might only need a refresher or a nudge in the right direction. These days I usually spelunk in the headers, and then hit the docs if I’m not sure what the headers are trying to tell me.