Render partial for model with nested attributes in another model - ruby-on-rails

Question

I have a rails application that models a house. house contains rooms and rooms have nested attributes for light and small_appliance. I have a calculator controller, which is how end users will access the application.
My problem is that I can't get the partial for adding rooms to render and submit correctly from calculator. The initial page lets the user enter house information, which is saved using save_house when submit is clicked. This also redirects the user to the add_rooms page, where they can add rooms to the house.
add_rooms displays correctly, but when I click submit, I get this error:
RuntimeError in Calculator#add_room
Showing app/views/calculator/add_rooms.html.erb where line #2 raised:
Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id
Extracted source (around line #2):
1: <div id="addRooms">
2: <p>House id is <%= #house.id %></p>
3:
4: <h3>Your rooms:</h3>
5: <% if #house.rooms %>
RAILS_ROOT: C:/Users/ryan/Downloads/react
Application Trace | Framework Trace | Full Trace
C:/Users/ryan/Downloads/react/app/views/calculator/add_rooms.html.erb:2:in `_run_erb_app47views47calculator47add_rooms46html46erb'
C:/Users/ryan/Downloads/react/app/controllers/calculator_controller.rb:36:in `add_room'
C:/Users/ryan/Downloads/react/app/controllers/calculator_controller.rb:33:in `add_room'
This is odd to me, because when add_rooms first renders, it shows the house_id. I don't understand why it isn't passed after the form is submitted.
Here's the code:
app/models/room.rb
class Room < ActiveRecord::Base
# schema { name:string, house_id:integer }
belongs_to :house
has_many :lights, :dependent => :destroy
has_many :small_appliances, :dependent => :destroy
validates_presence_of :name
accepts_nested_attributes_for :lights, :reject_if => lambda { |a| a.values.all?(&:blank?) }, :allow_destroy => true
accepts_nested_attributes_for :small_appliances, :reject_if => lambda { |a| a.values.all?(&:blank?) }, :allow_destroy => true
end
app/models/house.rb
class House < ActiveRecord::Base
has_many :rooms
# validation code not included
def add_room(room)
rooms << room
end
end
app/controllers/calculator_controller.rb
class CalculatorController < ApplicationController
def index
end
def save_house
#house = House.new(params[:house])
respond_to do |format|
if #house.save
format.html { render :action => 'add_rooms', :id => #house }
format.xml { render :xml => #house, :status => :created, :location => #house }
else
format.html { render :action => 'index' }
format.xml { render :xml => #house.errors, :status => :unprocessable_entity }
end
end
end
def add_rooms
#house = House.find(params[:id])
#rooms = Room.find_by_house_id(#house.id)
rescue ActiveRecord::RecordNotFound
logger.error("Attempt to access invalid house #{params[:id]}")
flash[:notice] = "You must create a house before adding rooms"
redirect_to :action => 'index'
end
def add_room
#room = Room.new(params[:room])
#house = #room.house
respond_to do |format|
if #room.save
flash[:notice] = "Room \"#...#room.name}\" was successfully added."
format.html { render :action => 'add_rooms' }
format.xml { render :xml => #room, :status => :created, :location => #room }
else
format.html { render :action => 'add_rooms' }
format.xml { render :xml => #room.errors, :status => :unprocessable_entity }
end
end
rescue ActiveRecord::RecordNotFound
logger.error("Attempt to access invalid house #{params[:id]}")
flash[:notice] = "You must create a house before adding a room"
redirect_to :action => 'index'
end
def report
flash[:notice] = nil
#house = House.find(params[:id])
#rooms = Room.find_by_house_id(#house.id)
rescue ActiveRecord::RecordNotFound
logger.error("Attempt to access invalid house #{params[:id]}")
flash[:notice] = "You must create a house before generating a report"
redirect_to :action => 'index'
end
end
app/views/calculator/add_rooms.html.erb
<div id="addRooms">
<p>House id is <%= #house.id %></p>
<h3>Your rooms:</h3>
<% if #house.rooms %>
<ul>
<% for room in #house.rooms %>
<li>
<%= h room.name %> has <%= h room.number_of_bulbs %>
<%= h room.wattage_of_bulbs %> watt bulbs, in use for
<%= h room.usage_hours %> hours per day.
</li>
<% end %>
</ul>
<% else %>
<p>You have not added any rooms yet</p>
<% end %>
<%= render :partial => 'rooms/room_form' %>
<br />
</div>
<%= button_to "Continue to report", :action => "report", :id => #house %>
app/views/rooms/_room_form.html.erb
<% form_for :room, #house.rooms.build, :url => { :action => :add_room } do |form| %>
<%= form.error_messages %>
<p>
<%= form.label :name %><br />
<%= form.text_field :name %>
</p>
<h3>Lights</h3>
<% form.object.lights.build if form.object.lights.empty? %>
<% form.fields_for :lights do |light_form| %>
<%= render :partial => "light", :locals => { :form => light_form } %>
<% end %>
<p class="addLink"><%= add_child_link "[+] Add new light", form, :lights %></p>
<h3>Small Appliances</h3>
<% form.object.small_appliances.build if form.object.small_appliances.empty? %>
<% form.fields_for :small_appliances do |sm_appl_form| %>
<%= render :partial => "small_appliance", :locals => { :form => sm_appl_form } %>
<% end %>
<p class="addLink"><%= add_child_link "[+] Add new small appliance", form, :small_appliances %></p>
<p><%= form.submit "Submit" %></p>
<% end %>
application_helper.rb
module ApplicationHelper
def remove_child_link(name, form)
form.hidden_field(:_delete) + link_to_function(name, "remove_fields(this)")
end
def add_child_link(name, form, method)
fields = new_child_fields(form, method)
link_to_function(name, h("insert_fields(this, \"#{method}\", \"#{escape_javascript(fields)}\")"))
end
def new_child_fields(form_builder, method, options = {})
options[:object] ||= form_builder.object.class.reflect_on_association(method).klass.new
options[:partial] ||= method.to_s.singularize
options[:form_builder_local] ||= :form
form_builder.fields_for(method, options[:object], :child_index => "new_#{method}") do |form|
render(:partial => options[:partial], :locals => { options[:form_builder_local] => form })
end
end
end
Thanks,
Ryan

Answer 1

Out of curiosity why not have house accept nested attributes for rooms. This would make your controller code simpler, as adding many rooms, lights and small appliances is as simple as just doing #house.update_attributes(params[:house]). However this is not an answer that helps, as you would still have your current problems if you made the change.
Your first error comes from the first line of app/views/calculator/_room_form.html.erb
<% form_for :room, :url => { :action => :add_room, :id => #house } do |form| %>
You're not giving form_for an object so the new_child_fields method called by add_child
_link is trying to call reflect_on_association on the Nil class.
The solution is change the line to
<% form_for :room, #house.rooms.build, :url => { :action => :add_room } do |form| %>
This lets you simplify your controller, because a room associated with a house is already being passed to it.
def add_room
#room = Room.new(params[:room])
#house = #room.house
respond_to do |format|
if #room.save
flash[:notice] = "Room \"#...#room.name}\" was successfully added."
format.html { render :action => 'add_rooms' }
format.xml { render :xml => #room, :status => :created, :location => #room }
else
format.html { render :action => 'add_rooms' }
format.xml { render :xml => #room.errors, :status => :unprocessable_entity }
end
end
rescue ActiveRecord::RecordNotFound
logger.error("Attempt to access invalid house #{params[:id]}")
flash[:notice] = "You must create a house before adding a room"
redirect_to :action => 'index'
end
I believe your second error is the same problem. However because you're calling a has_many accessor instead of getting a nil being generated, you're passing an empty array, which explains the difference in error messages. Again the solution is to build a light and small appliance before rendering if none exist yet.
<h3>Lights</h3>
<% form.object.lights.build if form.object.lights.empty? %>
<% form.fields_for :lights do |light_form| %>
<%= render :partial => 'rooms/light', :locals => { :form => light_form } %>
<% end %>
<p class="addLink"><%= add_child_link "[+] Add new light", form, :lights %></p>
<h3>Small Appliances</h3>
<% form.object.small_appliances.build if form.object.small_appliances.empty? %>
<% form.fields_for :small_appliances do |sm_appl_form| %>
<%= render :partial => 'rooms/small_appliance', :locals => { :form => sm_appl_form } %>
<% end %>
Your new error comes from this:
def new_child_fields(form_builder, method, options = {})
options[:object] ||= form_builder.object.class.reflect_on_association(method).klass.new
# specifically this line.
options[:partial] ||= method.to_s.singularize
options[:form_builder_local] ||= :form
form_builder.fields_for(method, options[:object], :child_index => "new_#{method}") do |form|
render(:partial => options[:partial], :locals => { options[:form_builder_local] => form })
end
end
new_child_fields is assuming that the _light partial is in the app/views/calculators folder
The solution is to either move the light and small_appliances partials to this folder or modify your helper methods to accept a partial option.