7

I'm trying to understand how the puts function fits in Ruby's "Everything is an object" stance.

Is puts is the method of a somehow hidden class/object? Or is it a free-floating method, with no underlying object?

13

I'm trying to understand how the puts function fits in Ruby's "Everything is an object" stance.

First off, puts is not a function. It's sole purpose is to have a side-effect (printing something to the console), whereas functions cannot have side-effects … that's the definition of "function", after all.

Ruby doesn't have functions. It only has methods. Thus, puts is a method.

Is puts is the method of a somehow hidden class/object?

No, it's just a boring old instance method of a boring old class. (Well, a boring old instance method of a boring old mixin, actually, but a mixin is just a class which abstracts over its superclass.)

Kernel is mixed into Object, which is the (default) superclass of all objects (modulo BasicObject, of course), thus, Kernel is a common superclass (or "supermixin", if you prefer) of (almost) all objects in Ruby.

Or is it a free-floating method, with no underlying object?

There is no such thing. A method is always associated with an object (the receiver of the message), that's what makes it a "method". (At least in OO parlance. In ADT-oriented languages, the word "method" means something slightly different.)

By the way, the easiest option is always to just ask Ruby herself:

method(:puts).owner
# => Kernel
  • 5
    ... functions can have side-effects. They're called impure functions. – amara May 30 '12 at 12:04
  • 1
    Thanks, very enlightening. I should have used the word sub-routine instead of function, I understand this was misleading. – gyin May 30 '12 at 14:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.