This module allows to create a virtual field from multiple fields

aggregate_field.rb

# = AggregateField
#
# This module allows to create a virtual field from multiple fields
#
# Example:
#
# class DummyClass
#   include AggregateField
#
#   attr_accessor :first_name, :last_name
#   aggregate_field :full_name, composed_of: [:first_name, :last_name], separated_by: ' '
# end
#
# Author : Bastien Gysler <basgys@gmail.com>
module AggregateField
  extend ActiveSupport::Concern

  DEFAULT_SEPARATOR = ' '.freeze

  module ClassMethods

    # Create a virtual field from different fields
    # 
    # Parameters:
    # - field_name (virtual field name)
    # - composed_of (list of fields aggregated)
    # - separated_by (separator) [optionnal]    
    def aggregate_field(field_name, options = {})
      options[:composed_of] and options[:composed_of].kind_of?(Array) or raise ArgumentError, "\"composed_of\" option must be given (Array)!"
      options[:separated_by] ||= DEFAULT_SEPARATOR

      define_method(field_name) do
        options[:composed_of].map{|field| public_send(field)}.compact.join(options[:separated_by])
      end
    end

  end

end