Undefined method in ActiveSupport concern

Question

I have a model that extends ActiveRecord::Base and includes a concern:

class User < ActiveRecord::Base
    include UserConcern

    def self.create_user()
        ...
        results = some_method()
    end

end

UserConcern is stored in the concerns directory:

module UserConcern
    extend ActiveSupport::Concern

    def some_method()
        ...
    end
end

I am getting a run-time error when I try to create a new user by calling the create_user method that looks like this:

undefined method 'some_method' for #<Class:0x000000...>

I have two questions about this:

1. Why is the some_method undefined? It seems to me that I am properly including it with the statement include UserConcern. Does it have something to do with my User class extending ActiveRecord::Base? Or maybe something to do with the fact that I am calling some_methods() from a class method (i.e. self.create_user())?

2. Why does the run-time error refer to #<Class:0x000000...> instead of to #<User:0x000000...>?

Answer 1

try it

models/concerns/user_concern.rb:

module UserConcern
  extend ActiveSupport::Concern

  def some_instance_method
    'some_instance_method'
  end

  included do
    def self.some_class_method
      'some_class_method'
    end
  end
end

models/user.rb:

class User < ActiveRecord::Base
  include UserConcern
  def self.create_user
    self.some_class_method
  end
end

rails console:

user = User.new
user.some_instance_method
# => "some_instance_method"

User.some_class_method
# => "some_class_method"

User.create_user
# => "some_class_method"

http://api.rubyonrails.org/classes/ActiveSupport/Concern.html