What's the difference between a method and a function?

function oop methods language-agnostic terminology
willc2 picture willc2 · Oct 1, 2008 · Viewed 759.1k times · Source

Can someone provide a simple explanation of methods vs. functions in OOP context?

Answer

Andrew Edgecombe picture Andrew Edgecombe · Oct 1, 2008

A function is a piece of code that is called by name. It can be passed data to operate on (i.e. the parameters) and can optionally return data (the return value). All data that is passed to a function is explicitly passed.

A method is a piece of code that is called by a name that is associated with an object. In most respects it is identical to a function except for two key differences:

  1. A method is implicitly passed the object on which it was called.
  2. A method is able to operate on data that is contained within the class (remembering that an object is an instance of a class - the class is the definition, the object is an instance of that data).

(this is a simplified explanation, ignoring issues of scope etc.)

Related questions

Why does Python code use len() function instead of a length method?

I know that python has a len() function that is used to determine the size of a string, but I was wondering why it's not a method of the string object. Update Ok, I realized I was embarrassingly mistaken. __len__() …

Read More
How can I call a static method on a variable class?

I'm trying to make some kind of function that loads and instantiates a class from a given variable. Something like this: <?php function loadClass($class) { $sClassPath = SYSPATH."/classes/{$class}.php"; if (file_exists($sClassPath)) { require_once($sClassPath); $class = $class::…

Read More
Can you alter a Javascript function after declaring it?

Let's say I have var a = function() { return 1; }. Is it possible to alter a so that a() returns 2? Perhaps by editing a property of the a object, since every function is an object? Update: Wow, thanks for all the responses. …

Read More