Validate presence of polymorphic parent

Question

I am developing a Rails 3.2 application with the following models:

class User < ActiveRecord::Base
  # Associations
  belongs_to :authenticatable, polymorphic         


        

Answer 1

I was able to get this to work by overriding the nested attribute setter.

class Physician
  has_one :user, as: :authenticatable
  accepts_nested_attributes_for :user

  def user_attributes=(attribute_set)
    super(attribute_set.merge(authenticatable: self))
  end
end

To DRY it up, I moved the polymorphic code to a concern:

module Authenticatable
  extend ActiveSupport::Concern

  included do
    has_one :user, as: :authenticatable
    accepts_nested_attributes_for :user

    def user_attributes=(attribute_set)
      super(attribute_set.merge(authenticatable: self))
    end
  end
end

class Physician
  include Authenticatable
  ...
end

For has_many associations, the same can be accomplished with a map:

class Physician
  has_many :users, as: :authenticatable
  accepts_nested_attributes_for :users

  def users_attributes=(attribute_sets)
    super(
      attribute_sets.map do |attribute_set|
        attribute_set.merge(authenticatable: self)
      end
    )
  end
end

class User
  belongs_to :authenticatable, polymorphic: true
  validates :authenticatable, presence: true
end

All that said, I think konung's last comment is correct - your example does not look like a good candidate for polymorphism.