Steffen Itterheim has compiled a complete list of those
Objective-C @ compiler directives:
I haven’t been able to find a list of all Objective-C @ compiler directives in one place. We all know the keywords like @interface and @implementation but others like @dynamic and @encode are lesser known, and possibly even much less understood.
You might also like this really nice Objective-C cheat sheet from Ray Wenderlich.