CODEWITHSUNDEEP
ruby-on-railsrubydatabaseactiverecord
Trần Kim Dự
Trần Kim Dự

Reputation: 6102

ActiveRecord: how to throw exception when reference key not exist

For example, I have two models:

class CheckInDetail < ApplicationRecord
  belongs_to :product
end

class Product < ApplicationRecord
end

For example, when I insert CheckInDetail, I add foreign key product_id to hash params. I tried use some non-exist product id and column product_id will be null. I want to throw exception when inserting like this.

There is a way that use validate on model for checking that field before inserting. But I think this will cost time (because I insert bunch of items) and not really necessary because client doesn't do that. (just in case something really went wrong).

Upvotes: 1

Views: 149

Answers (1)

oreoluwa
oreoluwa

Reputation: 5633

This is one of the benefits of relational databases, as you could add a foreign_key reference to your migration and everything should work perfectly. You could run a migration with rails g migration add_foreign_key_to_check_in_details

in the migration, you should add something like:

class AddForeignKeyToCheckInDetails < AR::Migration
  def change
    remove_foreign_key :check_in_details, :products
    add_foreign_key :check_in_details, :products, dependent: :delete
  end
end

With this in place all attempts to save a non existent product will fail. Also ensure to add a NOT NULL constraint to your product_id column, as attemts to save a check_in_detail with a null product_id will succeed. The update to the migration would look like:

change_column :check_in_details, :product_id, :integer, null: false

Let me know if that answers your question.

Upvotes: 1

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