Settings as pair value

setting.rb

# ---- Guardar configuraciones como clave-valor en la BD. ----
# Set
#     Setting.clave = valor
#     Setting[clave] = valor
# Get
#     Setting.clave
#     Setting[clave]
# Destroy
#     Setting.destroy(clave)

# == Schema Information
#
# Table name: settings
#
#  id         :integer          not null, primary key
#  var        :string(255)
#  value      :text
#  created_at :datetime
#  updated_at :datetime
#

class Setting < ActiveRecord::Base
  
  class SettingNotFound < RuntimeError; end
  
  class << self
    
    # get o set de una variable con la variable como nombre de método
    def method_missing(method, *args)
      method_name = method.to_s
      super(method, *args)
    rescue NoMethodError
      # set del valor a la variable
      if method_name[-1] == '='
        var_name = method_name.sub('=', '')
        value = args.first
        self[var_name] = value
      else
        # recuperar el valor de una variable
        self[method_name]
      end
    end

    # elimina la variable
    def destroy(var_name)
      var_name = var_name.to_s
      obj = object(var_name)
      raise SettingNotFound, "La variable \"#{var_name}\" no existe" if obj.nil?

      obj.destroy
      true
    end

    # accede a una variable a través de la notación []
    def [](var_name)
      object(var_name).try(:value)
    end

    # setea una variable a través de la notación []
    def []=(var_name, value)
      var_name = var_name.to_s

      record = object(var_name) || self.new(var: var_name)
      record.value = value
      record.save!

      value
    end

    def object(var_name)
      self.find_by(var: var_name.to_s)
    end
  end

end