How to add macro style methods to a rails model

ruby_macro_methds.rb

# Rails Concern
# models/concerns/nicknameable.rb
module Nicknameable
  extend ActiveSupport::Concern

  included do
    def self.nicknames(*args)
      define_method("nicknames") { args }
    end
    nicknames
  end
end

# /models/person.rb
class Person < ActiveRecord::Base
  include Nicknameable
  nicknames "foo", "bar"
end

# person = Person.new
# person.nicknames # => ["foo", "bar"]

# In pure Ruby
class Person
  def self.nicknames(*args)
    define_method(nicknames) { args }
  end
  nicknames :foo, :bar
end