Question

I have a list of items in a table and I’d like to create collections of those items in a new table. I’ve looked at has_many and has_many :through but I’m not sure those are the right choice and I’m not entirely sure how they’d work in my situation.

One special circumstance is that I want the items from the table to be identified by a unique field called typeID instead of the normal ID.

More information:

My model:

  create_table "products", :force => true do |t|
    t.integer  "typeID"
    t.string   "name"
    t.decimal  "basePrice",   :precision => 17, :scale => 4
    t.datetime "created_at",                                 :null => false
    t.datetime "updated_at",                                 :null => false
  end

I have a bunch of products and I need to have some of them bundled into packages (to sell as a bundle) that I can work with. The products will need to be able to be included in multiple different bundles.

Answer 1

I’d recommend a similar approach to Samiron’s if each product only belongs to a single package.

However, if that’s not the case, I’d recommend has_many :through instead. Here’s an example of that:

class Package
  has_many :product_listings
  has_many :products, :through => :product_listings

  # allows you to make convenient create/build calls like i do below
  accepts_nested_attributes_for :product_listings
end

class Product
  # defining these relations are only necessary if you want to be able to get all
  # packages a product exists in
  has_many :product_listings
  has_many :packages, :through => :product_listings
end

class ProductListing
  belongs_to :package
  belongs_to :product

  attr_accessible :package_id, :product_id
end

Then, in some view, you could do something like this:

Package.all.each do |package|
  <%= package.name %>  # or whatever attribute the package has
  package.products.each do |product|
    <%= product.name %>  # or whatever attribute the product has
  end
end

Edit

See the addition to the Package model.

Here’s how you’d add products to a package:

package = Package.create(:name => 'some package')

# Rails naming convention for attributes is snake_case, not camelCase (if you care) 
product = Product.create(:name => 'mouse', :base_price => 20.00)

package.product_listings.create(:product_id => product.id)