Rails 3: Uniqueness validation for nested fields_for

Question

A have two models, \"shop\" and \"product\", linked via has_many :through.

In the shop form there are nested attributes for multiple products, and I\'m having a litt

Answer 1

You could write a custom validator like

# app/validators/products_name_uniqueness_validator.rb
class ProductsNameUniquenessValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors[attribute] << "Products names must be unique" unless value.map(&:name).uniq.size == value.size
  end
end

# app/models/shop.rb
class Shop < ActiveRecord::Base
  validates :products, :products_name_uniqueness => true
end