gistfile1.rb

  def index
    @rooms = Room.includes :user
    result = []

    @rooms.each do |room|
      el1 = {}
      el2 = {}
      Room.column_names.each { |col| el1[col] = room.send col }
      User.column_names.each { |col| el2[col] = room.user.send col }
      result << el1.merge(user: el2)
    end
    
    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: result }
    end
  end