Ruby – Including a Ruby class from a separate file


For a while I had been including an entire class inside of a Ruby module. Apparently this is not what I am supposed to do. It appears that the point of a module is to store functions which can then be included as methods in a new class.

I don't want this. I have a class that I want to keep in a separate file which I can access from other files. How can I do this?


Best Solution

Modules serve a dual purpose as a holder for functions and as a namespace. Keeping classes in modules is perfectly acceptable. To put a class in a separate file, just define the class as usual and then in the file where you wish to use the class, simply put require 'name_of_file_with_class' at the top. For instance, if I defined class Foo in foo.rb, in bar.rb I would have the line require 'foo'.

If you are using Rails, this include often happens automagically

Edit: clarification of file layout

#file: foo.rb
class Foo
  def initialize
    puts "foo"


#file: bar.rb
require 'foo'

If you are in Rails, put these classes in lib/ and use the naming convention for the files of lowercase underscored version of the class name, e.g. Foo -> foo.rb, FooBar -> foo_bar.rb, etc.

As of ruby version 1.9 you can use require_relative, to require files relatively to the file you are editing.