Rails nested forms with pre-defined fields as checkboxes

Question

I'm making a hotel app that includes Room and RoomAttribute models. The two models have a many_to_many relationship between each other through a join table. The attributes for each model are as follows:

• Room – room_number, room_type (e.g. "deluxe" or "suite"), and price.
• RoomAttributes – name (e.g. "Wireless Internet", "Cable TV", "Bath Tub").

The user will first create a set of room attributes, so that these can be selected as checkboxes every time a new room is created. For example, some rooms may have wireless internet and some don't. The code for app/views/rooms/new.html.erb is (my apologies for using raw html).

<form action="<%= rooms_path %>" method="post">
  <input type="hidden" name="authenticity_token" value="<%= form_authenticity_token %>">

  <label for="room_number">Room Number:</label>
  <input type="text" name="room[room_number]" id="room_number"> <br>

  <label for="room_type">Type:</label>
  <input type="text" name="room[room_type]" id="room_type"> <br>

  <label for="price">Price:</label>
  <input type="text" name="room[price]" id="price"> <br>

  <label for="room_attributes">Attributes:</label>
  <ul>
    <% @room_attributes.each do |room_attribute| %>
      <li>
        <input type="checkbox" name="room[room_attributes_ids][]" value="<%= room_attribute.id %>"> 
        <%= room_attribute.name %>
      </li>
    <% end %>
  </ul>

  <input type="submit" value="Submit">
</form>

I'm using Rails 4 and I'd like to ask for advice on the following:

• Set up the form using form helpers or formtastic so that it already outputs all the pre-defined room attributes and users can simply select which attributes to include in the room via checkboxes.
• Write RoomController#create method for this so that it sets the nested RoomAttribute models as room attributes. Do I need accepts_nested_attributes_for :room_attributes in my app/models/room.rb?

• How to incorporate strong parameters in this scenario. I've read that I should use

  params.require(:room).permit(:room_number, :room_type, :price, room_attributes_attributes: [:id]) 
  

  but this is not working for me.

Thank you! :)

Answer 1

I was able to solve it by simply digging into the Rails 4 documentation. Every instance of my Room model has a method room_attribute_ids=. Notice that Rails singularized room_attributes to room_attribute and appended an _ids for the param, whereas my previous implementation used the pluralized one and the :name_of_associated_model_attributes => [:id] convention.

Thus I list the room attributes in new.html.erb as follows:

<label for="room_attributes">Attributes:</label>
<ul>
  <% @room_attributes.each do |room_attribute| %>
    <li>
      <input type="checkbox" name="room[room_attribute_ids][]" value="<%= room_attribute.id %>"> 
      <%= room_attribute.name %>
    </li>
  <% end %>
</ul>

Then in the controller I defined a private method to apply strong parameters for the nested attribute:

def room_params
  params.require(:room).permit(:room_number, :room_type, :price, :room_attribute_ids => [])
end