unknown attribute with polymorphic association - ruby-on-rails

Question

In my online shop I have tables Product and Size, also I think I need to add a table Restocking
Instead of updating a product, I guess It's better to have a Restocking table then I could track the dates where I added any new sizes, quantity, and why not the new prices (buying and selling)... and create stats...
Do you this it is correct?
Once a Restocking is created, the corresponding Product is updated with new quantity and price?
Well,
So it started this way:
#Product
has_many :sizes
accepts_nested_attributes_for :sizes, reject_if: :all_blank, allow_destroy: true
#Size
belongs_to :product
The Restocking table needs to have sizes attributes (like product)
I believe that I have to use polymorphic associations, but how I am supposed to update my schema , what should I add, remove?
So since I added the Restocking model, my models look like this:
#Product
has_many :sizes, inverse_of: :product, dependent: :destroy, as: :sizeable
has_many :restockings
accepts_nested_attributes_for :sizes, reject_if: :all_blank, allow_destroy: true
#Restocking
has_many :sizes, as: :sizeable
belongs_to :product
accepts_nested_attributes_for :sizes, reject_if: :all_blank, allow_destroy: true
#Size
belongs_to :product
belongs_to :restocking
belongs_to :sizeable, polymorphic: true, class_name: "Size"
schema.rb
create_table "sizes", force: :cascade do |t|
t.string "size_name"
t.integer "quantity"
t.bigint "product_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.integer "quantity_stock"
t.index ["product_id"], name: "index_sizes_on_product_id"
end
create_table "restockings", force: :cascade do |t|
t.bigint "product_id"
t.bigint "sizeable_id"
t.decimal "price", precision: 10, scale: 2
t.decimal "buying_price", precision: 10, scale: 2
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.index ["product_id"], name: "index_restockings_on_product_id"
t.index ["sizeable_id"], name: "index_restockings_on_sizeable_id"
end
create_table "products", force: :cascade do |t|
t.string "title", limit: 150, null: false
t.text "description"
t.bigint "category_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "color"
t.integer "user_id"
t.json "attachments"
t.string "brand"
t.string "ref"
t.decimal "price"
t.decimal "buying_price", precision: 10, scale: 2
t.index ["category_id"], name: "index_products_on_category_id"
end
At this point I have several errors, like
in ProductsController
def new
#product = Product.new
#product.sizes.build
end
error:
ActiveModel::UnknownAttributeError at /admin/products/new
unknown attribute 'sizeable_id' for Size.
Can you light me on the migrations I have to change?
Suggestions are welcome

Answer 1

You're almost there, to use polymorphic inside your Size model, you have to change the size resource, and add two attributes to the resource: sizeable_id and sizeable_type.
The sizeable_type is a string, indicates the class of the parent element, in your case, can be Product or Restocking, and sizeable_id indicates the element_id to find the parent element, your relations are correct, but you must add this elements to your Size, see the following:
One exemple of a migration to your case:
class AddSizeableToSize < ActiveRecord::Migration
def change
add_reference :sizes, :sizeable, polymorphic: true, index: true
end
end
On your Size model:
# app/models/size.rb
class Size < ActiveRecord::Base
belongs_to :sizeable, polymorphic: true
end
In your Product or Restocking model:
has_many :sizes, as: :sizeable
This is just a simple way to make your case works! If you want to know more about rails associations and polymorphism, can take a look in this link.