Rails: Creating a Multiple Model Form over n association levels - ruby-on-rails

Question

Can anyone tell me why the form at the end of this question isn't working like it should?
Save doesn't work
The select-helper doesn't select the
value according to the object #kid
The whole thing is based on Rails 2.2.2 and no, upgrading to Rails 2.3 to solve this problem isn't an option. :-)
I used this recipe to build the multiple model form.
# CLASS GRANDPARENT
class Grandparent < ActiveRecord::Base
has_many :parents
end
# CLASS PARENT
class Parent < ActiveRecord::Base
belongs_to :grandparent, :class_name => "Grandparent", :foreign_key => "grandparent_id"
has_many :kids
end
# CLASS KID
class Kid < ActiveRecord::Base
belongs_to :parent, :class_name => "Parent", :foreign_key => "parent_id"
# Virtual attribute setter for new self.parent.grandparent (Grandparent) attributes
def new_grandparent_attributes=(_gp_attributes)
self.parent.build_grandparent(_gp_attributes)
end
# Virtual attribute setter for existing self.parent.grandparent (Grandparent) attributes
def existing_grandparent_attributes=(_gp_attributes)
unless self.parent.grandparent.new_record?
attributes = _gp_attributes[self.parent.grandparent.id.to_s]
if attributes
self.parent.grandparent.attributes = attributes
else
self.parent.grandparent.delete(grandparent)
end
end
end
end
# CONTROLLER KIDS
class KidsController < ApplicationController
def new
#kid = Kid.new
end
def edit
#kid = Kid.find(params[:id])
end
def create
params[:kid][:new_grandparent_attributes] ||= {}
#kid = Kid.new(params[:kid])
end
def update
params[:kid][:existing_grandparent_attributes] ||= {}
#kid = Kid.find(params[:id])
end
end
# THIS IS THE MULTI-MODEL FORM USED IN THE VIEW
<% form_for(#kid) do |f| %>
<p>
<% new_or_existing = #kid.parent.grandparent.new_record? ? 'new' : 'existing' %>
<% prefix = "kid[#{new_or_existing}_grandparent_attributes][]" %>
<% fields_for prefix, #kid.parent.grandparent do |g_f| -%>
<p>
<%= g_f.label :, 'Grandparent Name' %><br />
<!-- THE FOLLOWING FORM DOESN'T CHANGE ACCORDING TO EXISTING #child -->
<%= #grandparents = Entity.find(:all, :order => :name)
g_f.collection_select(:name ,#grandparents, :id, :name)
%>
</p>
<% end %>
</p>
<p>
<%= f.label :name, "Kid Name" %><br />
<%= f.text_field :name %>
</p>
<%= submit_tag 'Go' %>
<% end %>

Answer 1

Well, correct me if I am wrong but it doesn't appear that you are actually saving the object anywhere. In your create and update actions you are calling new and then not saving it.
To rectify this you could do:
def create
params[:kid][:new_grandparent_attributes] ||= {}
#kid = Kid.new(params[:kid])
if #kid.save
# successful save logic here
else
#failed save logic here
end
end
def update
params[:kid][:existing_grandparent_attributes] ||= {}
#kid = Kid.find(params[:id])
if #kid.update_attributes(params[:kid])
#successful save logic here
else
#failed save logic here
end
end
Then in your select box you are trying to find every record of Entity, not those fields of Entity that are related to #kid. In order to do this you'll have to set up a relationship between kid and grandparent.
# CLASS GRANDPARENT
class Grandparent < ActiveRecord::Base
has_many :parents
has_many :grand_kids, :through => :parents
end
# CLASS PARENT
class Parent < ActiveRecord::Base
belongs_to :grandparent, :class_name => "Grandparent", :foreign_key => "grandparent_id"
has_many :kids
end
# CLASS KID
class Kid < ActiveRecord::Base
belongs_to :parent, :class_name => "Parent", :foreign_key => "parent_id"
belongs_to :grandparent
# ...
This way you can access a kid's grandparents through by #kid.grandparents. Then you can generate the select field:
<%= g_f.collection_select(:name ,#kid.grandparents, :id, :name) %>