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Table of Contents


“Method”, “message”, and “function” all (sort of) refer to the same thing in Objective-C.

A method is a section of code that we can call from elsewhere in our code.

Components to methods:

  1. Declaration
  2. Definition
  3. Invocation


Declaration- the act of informing other objects about a function's name, return type, and parameters.

Declarations for public methods are included in the header files of Objective-C objects.

Declarations for private methods are included in the Definition and do not need additional code. These methods can only be called within a class.

Declarations take the form:


A dash at the start indicates a instance method. Can only be called on an instantiated object. When creating a method, always use a dash unless you have some overriding reason.

A plus sign at the start indicates a class method. Can only be called on the class itself, commonly used as custom initialization method.


Definition- writing the code that executes/is contained within the method. Known as the method body.

Defining a Method Return Type: A method may return a value. The return_type is the data type of the value the function returns. Some methods perform the desired operations without returning a value. In this case, the return_type is the keyword void.

Method Name: This is the actual name of the method. The method name and the parameter list together constitute the method signature.

Arguments: A argument is like a placeholder. When a function is invoked, you pass a value to the argument. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the arguments of a method. Arguments are optional; that is, a method may contain no argument.

Joining Argument: A joining argument is to make it easier to read and to make it clear while calling it.

Method Body: The method body contains a collection of statements that define what the method does.

Declaration Method declaration is required when you define a method in one source file and you call that method in another file. In such case you should declare the function at the top of the file calling the function.

ios-labs-s14/basics-methods.1392657771.txt.gz · Last modified: 2014/02/17 11:22 by mbarboi