CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-5
Charles Smith
Charles Smith

Reputation: 3289

Create Join Table for a belongs_to association in Rails 5

I have a products model and a variations model as a belongs_to association. There are some variations that absolutely belong to a single product, but there are others that can belong to many products. Can I create a join table on a belongs_to association like in a has_and_blongs_to_many association?

My Models Currently

product.rb

class Product < ApplicationRecord
  has_many :variations, dependent: :destroy
  has_and_belongs_to_many :categories
  has_and_belongs_to_many :subcategories

  include FriendlyId
  friendly_id :name, use: :slugged

  def should_generate_new_friendly_id?
    name_changed?
  end
end

variation.rb

class Variation < ApplicationRecord
    has_and_belongs_to_many :categories
    has_and_belongs_to_many :subcategories
    belongs_to :product

    include FriendlyId
    friendly_id :name, use: :slugged

    def should_generate_new_friendly_id?
        name_changed?
    end
end

Upvotes: 0

Views: 1500

Answers (1)

Ziv Galili
Ziv Galili

Reputation: 1445

From Rails guides association basics - the belongs_to association:

A belongs_to association sets up a one-to-one connection with another model, such that each instance of the declaring model "belongs to" one instance of the other model.

When you do the belong_to :product association on the Variation model, it expect to have a field named product_id which will point to the associated product.

use example:

variation = Variation.first
product = variation.product # this line will get the product which is associated to the variation by the product_id column.

Since it can hold only one integer (one product id) the best option is to restructure your code. It makes no sense to use a "belong_to" as "has_many" association.

You need to change the association to some king of many to many association.

To chose the best option for you, read and learn the differences in the Rails guides - Association Basics

*** Make sure you won't lose your data when changing the association:

Idea of doing that:

  1. Create the join table
  2. Copy the info from your variations table (the variation.id and the associated product_id)
  3. Start using the new association

(You can probably copy the data in the migration file, just search how to do it)

Upvotes: 1

Related Questions