How is method being called outside of Module

at act_as_votable.rb is where the magic happens. at line 13 you can see ActiveRecord::Base.extend ActsAsVotable::Extenders::Votable. extend method here will inject ActsAsVotable::Extenders::Votable methods into ActiveRecord::Base class methods.

since Post inherits from ActiveRecord::Base which has ActsAsVotable module methods injected as class methods, Post can call acts_as_votable directly.

When module is loaded, it is extended to ActiveRecord::Base: https://github.com/ryanto/acts_as_votable/blob/599995f7ec5aa0f8a04312768fc956e9003d32d4/lib/acts_as_votable.rb

so, methods in module are available as class methods of ActiveRecord::Base class.

For more info about include/extend, you can check the article here:

https://yehudakatz.com/2009/11/12/better-ruby-idioms/

When you first add acts_as_votable gem it extends ActiveRecord::Base with methods defined in ActsAsVotable::Extenders::Votable module, its pretty common pattern to use modules as mixins mixins.

This initialization is done with this line:

ActiveRecord::Base.extend ActsAsVotable::Extenders::Votable

in lib/acts_as_votable.rb file

in other words methods inside ActsAsVotable::Extenders::Votable will be available as class methods to ActiveRecord::Base along with its inheritance chain.

the acts_as_votable in the post model is the execution of the method defined in the Votable module, which usually called a macro. It's a class method that defines another instance methods in that model. It has the same idea behind the has_many, belongs_to, .... macros.

macros

extend

What allows this to be run without calling the modules?

It works because:

• Ruby uses self if you don't specify an explicit receiver
• the class body is evaluated in the context of your class (self is Post)
• your Post class inherits from ActiveRecord::Base
• the gem adds acts_as_votable as a class method to ActiveRecord::Base

When you write:

class Post < ActiveRecord::Base
  acts_as_votable
end

it basically means:

class Post < ActiveRecord::Base
  self.acts_as_votable
end

which is actually:

class Post < ActiveRecord::Base
  Post.acts_as_votable
end

which could be rewritten as:

class Post < ActiveRecord::Base
end

Post.acts_as_votable

The above isn't specific to the gem. Within the class body, you can call any of your class' class methods directly. You might know:

class Foo
  attr_accessor :bar
end

That's not some special keyword – attr_accessor is a regular (class) method. The same applies to all the Rails DSL methods like has_many, validates or after_save.