How to update my Users/Products association - ruby-on-rails

Question

I'm trying to create an app to share or give products. So I have two models : User and Product.
A user can have many products, as an owner or as a borrower. A product has only one owner and only one borrower.
First I did something like that :
> rails generate model User name:string
class User
has_many :owned_products, class_name: "Product", foreign_key: "owner_id"
has_many :borrowed_products, class_name: "Product", foreign_key: "borrower_id"
end
> rails generate model Product name:string owner_id:integer borrower_id:integer
class Product
belongs_to :owner, class_name: "User", foreign_key: "owner_id"
belongs_to :borrower, class_name: "User", foreign_key: "borrower_id"
end
I added in my Product controller a security filter that enable the update method only for product's owner. But when I want to change the product's borrower, I have some kind of a problem, because the borrower is never the owner, so the product can not be updated.
So now I'm wondering if I should not take the foreign_key out of my products model, in order to dissociate the update action of a user on his own product, and the update action of a user to borrow a product that don't belongs to him...
> rails generate model User name:string
class User
has_many :properties
has_many :loans
has_many :owned_products, through: :properties
has_many :borrowed_products, through: :loans
end
> rails generate model Property owner_id:integer owned_product_id:integer
class Property
belongs_to :owner, class_name: "User", foreign_key: "user_id"
belongs_to :owned_product, class_name: "Product", foreign_key: "product_id"
end
> rails generate model Loan borrower_id:integer borrowed_product_id:integer
class Loan
belongs_to :borrower, class_name: "User", foreign_key: "user_id"
belongs_to :borrowed_product, class_name: "Product", foreign_key: "product_id"
end
> rails generate model Product name:string
class Product
has_one :property
has_one :loan
has_one :owner, through: :property
has_one :borrower, through: :loan
end
What do you think about it ?

Answer 1

Since borrowed products and owned products are the same type of object with the same list of attributes, but differ only in behavior, I would use single table inheritance for Product.
Migrations:
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
# ...
t.timestamps
end
end
end
class CreateProducts < ActiveRecord::Migration
def change
create_table :products do |t|
t.integer :ownerable_id
t.string :ownerable_type
# ...
t.timestamps
end
end
end
Models:
class User < ActiveRecord::Base
has_many :products, :as => :ownerable
end
class Product < ActiveRecord::Base
belongs_to :user, :polymorphic => true
end
class OwnedProduct < Product
end
class BorrowedProduct < Product
end
The benefit of this approach is that you can just define the appropriate behavior in each model without asking it if it's "owned" or "borrowed." Just tell your models what to do and leave the decisions up to each object to do the right thing.