gistfile1.rb

 def update_record
    json_data = JSON.parse(params["record"]["json_body"])
    data = CustomData.where(:id => params["record"]["id"], :application_id => @current_app.id).first
    authorize! :update, data
    data.update_attributes typify_hash(json_data)

    if json_data["user_id"] != data.user_id
      begin
        user = User.find(json_data["user_id"].to_i)
        data.user_id = user.id if (user.account_id == @current_user.account_id)
      rescue
      end
    end

    if data.save
      render :json => {:success => true}
    else
      render :json => {:success => false, :message => data.errors.full_messages.first}
    end
  rescue JSON::ParserError
    render :json => {:success => false, :message => "Parse error"}
  end