Custom non-db attributes in rails model not returned to jquery callback

I have the following model

class Game < ActiveRecord::Base

  # Associations
  belongs_to :black_member,         :class_name => "Member"
  belongs_to :white_member,         :class_name => "Member"
  belongs_to :current_move_member,  :class_name => "Member"
  belongs_to :game_requests, :foreign_key => "game_request_id"

  #Validations
  #attr_accessible :opponent_nickname, :current_member_id

  # Instance methods
  attr_accessor :opponent_nickname, :current_member_id

  def setup
    if self.white_member_id == self.current_member_id
      self.opponent_nickname = "test"
    end
  end

end

My controller:

# POST /games/setup.json 
  def setup

    @game = Game.find(params[:id])
    @game.current_member_id = currentmember.id
    @game.setup

    respond_to do |format|
      format.json { render :json => @game }
    end

  end

And my js function that sends & receives ajax request to controller:

// Setup all initial game details on game startup

    SITE.Game.LoadGameDetails = function() {

      gameId = $(".edit_game").attr("id").split('_')[2];

      $.post('/games/setup', {id: gameId},
        function(result) { 
          console.log("opp = " + result.opponent_nickname);
        }
      ,"json");
    }

For some reason my ajax call only seems to be return game attributes that are automatically generated by activeRecord. It doesn't seem to be sending back the 'opponent_n开发者_JAVA百科ickname'.

Any ideas why?

Thanks

---

Try this:

render :json => @game.to_json(:methods => :opponent_nickname)

The default json serializer comes from ActiveRecord, you need to add the new attribute to the json representation of the object.