Rails - Validate Nested Attributes Uniqueness with scope parent of parent

Question

I have a problem with the scoped uniqueness validation in Rails for nested attributes with a parent of parent.

Background

I have a rails 4 appl

Answer 1

A better option in terms of performances is described below. It is tested and works just fine.

Why?

Mapping emails can consume a lot of ressources when a lot of emails are at stake, so its better to perform the scope directly with the database.

How?

Cashing the account_id in the EmailAddress model and performing a before validation method.

1) Create a migration :

change_table :email_addresses do |t|
  t.references :account, index: true
end
add_index :email_addresses, [:account_id, :email], unique: true

2) Migrate

3) Update the EmailAddress model

#app/models/email_address.rb

class EmailAddress < ActiveRecord::Base
  belongs_to :contact, inverse_of: :email_addresses
  belongs_to :account

  validates :label, presence: true
  validates :contact, presence: true
  validates_email_format_of :email
  validates_uniqueness_of :email, allow_blank: false, scope: :account

  before_validation do
    self.account = contact.account if contact
  end

end