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

Question

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

Answer 1

They're often interchangeable, but a method usually refers to a subroutine inside a class, and a function usually refers to a subroutine outside the class. for instance, in Ruby:

# function
def putSqr(a)
   puts a ** 2
end


class Math2
   # method
   def putSqr(a)
      puts a ** 2
   end
end

In Java, where everything (except package and import statements) must be inside the class, people almost always refer to them as "methods".

Answer 2

Historically, there may have been a subtle difference with a "method" being something which does not return a value, and a "function" one which does.Each language has its own lexicon of terms with special meaning.

In "C", the word "function" means a program routine.

In Java, the term "function" does not have any special meaning. Whereas "method" means one of the routines that forms the implementation of a class.

In C# that would translate as:

public void DoSomething() {} // method
public int DoSomethingAndReturnMeANumber(){} // function

But really, I re-iterate that there is really no difference in the 2 concepts. If you use the term "function" in informal discussions about Java, people will assume you meant "method" and carry on. Don't use it in proper documents or presentations about Java, or you will look silly.

Answer 3

Function - A function in an independent piece of code which includes some logic and must be called independently and are defined outside of class.

Method - A method is an independent piece of code which is called in reference to some object and are be defined inside the class.

Answer 4

I know many others have already answered, but I found following is a simple, yet effective single line answer. Though it doesn't look a lot better than others answers here, but if you read it carefully, it has everything you need to know about the method vs function.

A method is a function that has a defined receiver, in OOP terms, a method is a function on an instance of an object.

Answer 5

Let's not over complicate what should be a very simple answer. Methods and functions are the same thing. You call a function a function when it is outside of a class, and you call a function a method when it is written inside a class.

Answer 6

A very general definition of the main difference between a Function and a Method:

Functions are defined outside of classes, while Methods are defined inside of and part of classes.