Deeply Nested Resource

Question

I have a deeply nested resource. Currently everything works fine, except when I crate a SONG. For some reason it does not store the ARTIST_ID in the database (shows up as NIL). Can someone please help me, I am a newb.

The first nested stores the ARTIST_ID in the ALBUMS table...

ROUTES.RB

resources :artists do
  resources :albums do
    resources :songs
  end
end

SONGS_CONTROLLER

class SongsController < ApplicationController

  respond_to :html, :js

  def index
    @artist = Artist.find(params[:artist_id])
    @album = Album.find(params[:album_id])
    @songs = @album.songs.all
  end

  def create
    @artist = Artist.find(params[:artist_id])
    @album = Album.find(params[:album_id])
    @song = @album.songs.create(params[:song])
      if @song.save
        redirect_to artist_album_songs_url
        flash[:success] = "Song Created."
      else
        render 'new'
      end
  end

  def new
    @artist = Artist.find(params[:artist_id])
    @album = Album.find(params[:album_id])
    @song = Song.new
  end

end

MODELS

class Artist < ActiveRecord::Base
  attr_accessible :name

  has_many :albums
  has_many :songs

end

class Album < ActiveRecord::Base
  attr_accessible :name, :artist_id

  belongs_to :artist
  has_many :songs

end

class Song < ActiveRecord::Base
  attr_accessible :name, :album_id, :artist_id

  belongs_to :albums

end

VIEW (CREATE, FOR SONGS)

<div class="container-fluid">
  <div class="row-fluid">

    <%= form_for ([@artist,@album, @song]), :html => { :multipart => true } do |f| %>
      <%= render 'shared/error_messages', object: f.object %>

      <%= f.text_field :name, placeholder: "name", :class => "input-xlarge"%>

      <%= f.submit "Create Song", class: "btn btn-primary"%>

    <% end %>

  </div>

</div>

Answer 1

IT looks like you're not setting the artist_id on the song anywhere. You are doing it right though - with a album_id and artist_id, you have to pick one of those as the parent. It's as though you are caching the artist_id on the song.

I think I would keep things they way you are doing it but add this to the model.

class Song < ActiveRecord::Base

  before_save :ensure_artist_id


  def ensure_artist_id
    self.artist_id = self.album.artist_id
  end

end

The other option is to set it in the controller explicitly

  def create
    @artist = Artist.find(params[:artist_id])
    @album = Album.find(params[:album_id])
    @song = @album.songs.create(params[:song].merge(:artist_id => @artist.id)
      if @song.save
        redirect_to artist_album_songs_url
        flash[:success] = "Song Created."
      else
        render 'new'
      end
  end

But that doesn't feel as clean and may be repeated in other controller methods. It's nicer to have it in the model.