Question

INTRO

model A

carname.rb

    class Carname < ActiveRecord::Base
        belongs_to :car
        has_many :carmodels, :dependent => :destroy
...

model B

carmodel.rb

    class Carmodel < ActiveRecord::Base
      belongs_to :carname
      belongs_to :car
...

carname fields: id, name

carmodel fields: id, name, carname_id

The problem:

I add a car name for ex BMW, then I can add carmodels for ex 3 series and select that this belongs to BMW. Works good in different views, but I want it to display the carmodels in the index view of carname, something like this

in http://www.whateverdomain.com/carnames

BMW  
       3 series
       5 series
       7 series

Mercedes
       E class
       S class
       C class

I have carnames displayed, not a big deal:

<% @carnames.each do |carname| %>
  <%= carname.name %>
<% end %>

but I can’t think off how to add models nex to it.
In carmodels index view I managed to display each carmodels with the carname that it belongs_to next to the carmodel

<% @carmodels.each do |carmodel| %>
      <%= carmodel.name %>
      <%= carmodel.carname.name %>
      <%= link_to 'Edit', edit_carmodel_path(carmodel) %>
      <%= link_to "Delete", carmodel, :confirm => 'Are you sure?', :method => :delete %>
  <% end %>

so in this html on screen looks like

3 series | BMW
5 series | BMW
7 series | BMW
C class  | Mercedes
E class  | Mercedes
etc..

if any other info is needed I’ll share it. Thank you for your time.

Answer 1

Try this code in your carnames/index.html.erb file:

<% @carnames.each do |carname| %>
    <h1><%= carname.name %></h1>
    <ul>
    <%- carname.carmodels.each do |carmodel| %>
        <li><%= carmodel.name %></li>
    <%- end %>
    </ul>
<% end %>

It will add every carname and their car models as an unordered list.

Edit: If you want to display carmodel.name | carname.name you can do:

<% @carnames.each do |carname| %>
    <ul>
    <%- carname.carmodels.each do |carmodel| %>
        <li><%= carmodel.name %> | <%= carname.name %></li>
    <%- end %>
    </ul>
<% end %>

Note: Why does a Carname belong to a Car? Wouldn’t it be easier to assign a name attribute to the Car class?