Following the instance variable declarations are the method declarations. Like standard C functions, methods in Objective-C have a return type and can take arguments. Additionally, methods can either be class methods or instance methods. Class methods can only be performed by the class object discussed above, and instance methods can be performed by any object of the class. A plus sign before the method name indicates that the method is a class method.
Arguments follow colons and multiple arguments are separated by the argument name and a space.
Like method return types, argument data types are also enclosed in parentheses before the name of the argument. For a class to link to a superclass you must import the superclass's interface file, which usually is the superclass name followed by a .h . The implementation file is where the meat of your class is coded. Remember now that the interface file is where your class is described, and this is the description programmers are to use to incorporate your class into their code. The implementation file is where you do your work.