Fun with Objective-C

Simple: because if you left it off, it wouldn’t be an NSString*. It’d be a char *. Any time you see the @ symbol in Objective-C code, you can know that it’s so that the compiler can do something special there that C doesn’t natively support.

So with that in mind, we have:

• @catch: declare a scope for catching a thrown execution
• @class: forward declare a class
• @compatibility_alias: specify an alias for a class name
• @dynamic: specify that property accessors will by dynamically implemented at runtime
• @encode: ask for a character array representing the type of a variable
• @end: close an interface declaration or an implementation block
• @finally: declare code that will be executed after an @try and/or @catch block execute
• @implementation: implement a class definition
• @interface: define a class API (also used for categories and class extensions)
• @optional: declare the optional nature of protocol methods
• @package: declare the scope of ivars
• @private: declare the scope of ivars
• @property: declare a class property
• @protected: declare the scope of ivars
• @protocol: declare a list of methods that conforming objects might implement
• @public: declare the scope of ivars
• @required: declare the required nature of protocol methods
• @selector: declare the the stuff that immediately follows in the parentheses is a method name
• @synchronized: declare a section of code that is atomic
• @synthesize: direct the compiler to generate accessor methods for properties (that you haven’t implemented yourself)
• @throw: throw an NSException
• @try: begin a block in which an exception might be thrown
• @"": declare a constant string

That’s all I can remember off the top of my head. I’m sure I’ve forgotten one or two. A more complete list (with better explanations) can be found in the documentation.