Question

I’m trying to make a form to set values to two children objects through has_one (with :class_name option) and belongs_to relation. However, when I input and submit values through the form, both children objects have the same value even if I input different values.

I have the these two models.
(two children objects above indicates “origin” and “destination” whose class names are “Place”)

class Route < ActiveRecord::Base
  attr_accessible :name, :destination_attributes, :origin_attributes                                            
  has_one :origin, :class_name=>"Place"
  has_one :destination, :class_name=>"Place"
  accepts_nested_attributes_for :origin, :destination
end

class Place < ActiveRecord::Base                                                                                                                                              
  attr_accessible :address, :lat, :lng, :name, :route_id
  belongs_to :route, :foreign_key => "route_id"
end

And made form using partial like following.

routes/_form.html.erb

<%= form_for(@route) do |f| %>
  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
    <br />
    <%= render :partial => "places/nested_places_form", :locals => {record_name: :origin, place_object: @route.origin, parent_form: f} %>
    <br />
    <%= render :partial => "places/nested_places_form", :locals => {record_name: :destination, place_object: @route.destination, parent_form: f} %>
  </div>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

places/nested_places_form.html.erb

 <%= parent_form.fields_for record_name, place_object  do |t| %>                                                                                                               
  <%= record_name %>

  <% if place_object.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@place.errors.count, "error") %> prohibited this place from being saved:</h2>

      <ul>
      <% @place.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= t.label :name %><br />
    <%= t.text_field :name %>
  </div>
  <div class="field">
    <%= t.label :lat %><br />
    <%= t.text_field :lat %>
  </div>
  <div class="field">
    <%= t.label :lng %><br />
    <%= t.text_field :lng %>
  </div>
<% end %>                                                                                                                                                                     

Like I mentioned, the attributes of origin and destination always end up the same even when I put different values in blanks and submit from form.

How can I make this work?

Answer 1

Somehow you’ll need to differentiate between origin and destination in the database. If they both have the same class and are stored in the same table, there’s nothing to tell them apart. If you don’t want to change the existing relationships, you might need to use STI for this and make the origin and destination different classes:

class OriginPlace < Place
end

class DestinationPlace < Place
end

class Route < ActiveRecord::Base
  ...
  has_one :origin, :class_name=>"OriginPlace"
  has_one :destination, :class_name=>"DestinationPlace"
  ...
ene

This will require a type field in the places table.