Using AlterEgo with ActiveRecord

Today after finding the gem AlterEgo and falling in love with the API, @chendo and I came to a sad realisation that its beauty was skin-deep. It seems it is not ActiveRecord-aware and overrides #state and #state= on your models. This means that your state column goes untouched and your models are always in the default state.

To get around this, @chendo and I hacked together this little monkey patch which does two things:

It adds question methods for each of your defined states. So if you have states: active, inactive, and banned on your User model, your instances will have #active?, #inactive?, and #banned?
It properly sets and gets the state of the row and loads it into AlterEgo.

Here is the code:

module AlterEgo
  def self.included(base)
    base.instance_eval do

      # This will allow us to define a question method for each state in a class
      # For instance if user has states :active and :inactive, methods active? and inactive?
      # will be defined when first called
      def method_missing_with_states(method, *args, &block)
        begin
          method_missing_without_states(method, *args, &block)
        rescue NoMethodError => e
          state_found = false
          result = nil

          base.states.keys.each do |state|
            if method.to_s == "#{state}?" && !state_found
              self.class.send :define_method, "#{state}?" do
                self.state == state
              end
              state_found = true
              result = self.__send__(method)
            end
          end
          raise(e) unless state_found
          result
        end
      end
      alias_method_chain :method_missing, :states

      # state setter to write to database
      define_method :state= do |value|
        write_attribute(:state, value.to_s)
      end

      # state getter to read from database
      define_method :state_with_active_record do
        (read_attribute(:state) || (self.state = state_without_active_record)).to_sym
      end
      alias_method_chain :state, :active_record
    end
  end
end

⚛ Be Genius

Bo Jeanes

Using AlterEgo with ActiveRecord

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