gistfile1.rb

class SomeModel < ActiveRecord::Base
  def some_method
    raise NotImplementedError
  end
end

module Api::V1::SomeModelMethods
  def some_method
    return {:blah => 1}
  end
end

class Api::V1::SomeController < Api::V1::ApplicationController
  class SomeModel
    include Api::V1::SomeModelMethods
  end

  def index
    render :json => SomeModel.all.map(&:some_method).to_json
  end
end