Calling Objective-C methods-Collection of common programming errors

The first sends a message to an object and so does the second. In almost all cases, you should use the first. It’s quicker and clearer. However, the second has its uses. For instance, you can use it in a situation where you would need to supply a call back.

Another powerful use is in combination with NSSelectorFromString(). You can literally decide what message to use at run time based on a string in a configuration file or from user input (don’t forget to validate it!). You can even build selector names using NSString -stringWithFormat: etc. For instance, this parser kit uses the technique to inform the program when parser rules have been matched.