Render a partial with a collection through multiple levels of has_many associations

Question

I am trying to show a collection of orders that belongs to a sellers products posts

the buyer is the user_id in the order, the seller is the user_id in the product

Quickly:
A user has many products
A product has many postings (to bring products to multiple events)
A post has many orders (other users can order)

Here's my code

        class User < ActiveRecord::Base
          # Include default devise modules. Others available are:
          # :token_authenticatable, :encryptable, :confirmable, :lockable, :timeoutable and :omniauthable
          devise :database_authenticatable, :registerable,
                 :recoverable, :rememberable, :trackable, :validatable

          # Setup accessible (or protected) attributes for your model
          attr_accessible :name, :email, :password, :password_confirmation, :remember_me,
                          :bio, :reason, :barter

                          #:email, :name, :bio, :reason, :barter, :

          has_many :products, :dependent => :destroy
          has_many :posts, :dependent => :destroy
          has_many :orders, :dependent => :destroy

            class Product < ActiveRecord::Base
                belongs_to :user
                belongs_to :club
                belongs_to :category
                has_many :posts, :dependent => :destroy

            class Post < ActiveRecord::Base
                      belongs_to :product, :include => [:user]
                belongs_to :event
                has_many :orders, :dependent => :destroy
                accepts_nested_attributes_for :orders

            class Order < ActiveRecord::Base
                belongs_to :user
                belongs_to :post
#schema
  create_table "orders", :force => true do |t|
    t.float    "quantity"
    t.float    "order_price"
    t.integer  "post_id"
    t.integer  "user_id"
    t.boolean  "payment_received"
    t.integer  "mark_for_buyer"
    t.string   "comment_for_buyer"
    t.integer  "mark_for_seller"
    t.string   "comment_for_seller"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "orders", ["post_id"], :name => "index_orders_on_post_id"
  add_index "orders", ["user_id"], :name => "index_orders_on_user_id"

  create_table "posts", :force => true do |t|
    t.float    "quantity"
    t.datetime "deadline"
    t.integer  "product_id"
    t.integer  "event_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "products", :force => true do |t|
    t.string   "title"
    t.text     "desc"
    t.text     "ingredients"
    t.float    "deposit"
    t.float    "cost"
    t.string   "units"
    t.float    "quantity"
    t.float    "deadline_hours"
    t.boolean  "presell_option"
    t.integer  "user_id"
    t.integer  "category_id"
    t.integer  "club_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

orders/index.html.erb

        #this one works beautifully 
        <%= render :partial => "order", :collection => @orders.find_all_by_user_id(current_user.id), :locals => {:order => @order}  %>
        #this one doesn't work (has_many association resources have been tricky for me)
        <%= render :partial => "order", :collection => @orders.where(:post => {:product  => {:user_id => current_user.id}}) , :locals => {:order => @order}  %>

orders/_order.html.erb

  
    <%= order.user.name %>
    <%= order.post.product.user.name %>
    <%= link_to order.post.product.title, order.post %>
    <%= number_to_currency order.order_price %>
    <%= order.quantity %>
    <%= order.updated_at.to_formatted_s(:short) %> 
    <%= order.payment_received %>
    <%= link_to 'Show', order %>
    <%= link_to 'Edit', edit_order_path(order) %>
    <%= link_to 'Destroy', order, :confirm => 'Are you sure?', :method => :delete %>

Now, one collection works great, where the order has a user_id field, it collects the user that made the order and shows all the correct orders. The other collection doesn't work, and I'm getting this error:

Error

ActiveRecord::StatementInvalid in Orders#index - No attribute named `user_id` exists for table `product`

But there IS a 'user_id' field in the 'product' table. I am able to call this in cancan to limit management of orders to the user who owns the product that is ordered, and works beautifully

can :update, Order, :post => {:product => {:user_id => user.id }}

Any insight is much appreciated!

thejonster · Accepted Answer

I've found the trick is this gem http://rubygems.org/gems/nested_has_many_through which can do something like this:

class Author < User
  has_many :posts
  has_many :categories, :through => :posts, :uniq => true
  has_many :similar_posts, :through => :categories, :source => :posts
  has_many :similar_authors, :through => :similar_posts, :source => :author, :uniq => true
  has_many :posts_of_similar_authors, :through => :similar_authors, :source => :posts, :uniq => true
  has_many :commenters, :through => :posts, :uniq => true
end

class Post < ActiveRecord::Base
  belongs_to :author
  belongs_to :category
  has_many :comments
  has_many :commenters, :through => :comments, :source => :user, :uniq => true
end

This has super-simplified my queries and collections.

This is all the code I ended up needing. I'm told the gem nested_has_many_through will be standard in Rails 3.1

User model

  has_many :products, :dependent => :destroy
  has_many :product_posts, :through => :products, :source => :posts, :uniq => true
  has_many :food_orders, :through => :product_posts, :source => :orders, :uniq => true

OrdersController

 @orders_for_my_products = current_user.food_orders.all

Orders index

<%= render :partial => "order", :collection => @orders_for_my_products, :locals => {:order => @order}  %>

This returns the deep nested data via relationships using minimal code. I sure hope its efficient, but at least my sanity is spared!