How do you instantiate Rails models with polymorphic association/validations on both sides?

Question

Banging my head on this problem for the past 2 hours. I have these two classes which are polymorphically linked. Doctors have doctor-y stuff in them and Users handle the web component (email addresses, devise, etc). A Doctor is a User.

The reason is there are different User classes (Nurses, MedicalInstitutions), all requiring their own fields, but are linked together by the fact that they are users. So I chose polymorphic association in this case.

The problem is I cannot seem to instantiate both of them because both of them doesn't get saved. Assume an empty database how exactly do I create both of them because they need each other? Is there a way to "save both" at the same time.

class User < ActiveRecord::Base
  rolify
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  validates_presence_of :profile

  belongs_to :profile, polymorphic: true
end

class Doctor < ActiveRecord::Base
  has_one :user, as: :profile, dependent: :destroy
  accepts_nested_attributes_for :user

  validates_presence_of :user

  # doctor-specific code here

  delegate :email, :password, to: :user
end

class Nurse < ActiveRecord::Base
  # has_one, accepts... same as doctor. nurse-specific code here
end

I'd also appreciate it if someone can solve how to instnantiate this in FactoryGirl.

Aside: I've seen this, but they don't have validations on both sides.

Answer 1

You can just skip the validation for your first record:

your_record.save(validate: false)

EDIT:

Actually, you don't need to skip the validation. The reason it isn't working is probably because validates_presence_of checks to see if the associated object exists in the database. So for Doctor, Nurse, etc (the has_many side) it is okay to do this because those tables are not storing the user_id. But you should change the User model's validation to check for:

validates :profile_id, presence: true

This will ensure that the profile_id attribute is assigned, even if the Profile (Doctor, Nurse, etc) does not exist yet. You must create the objects in the proper order though:

u = User.new
d = Doctor.new
u.profile = d
u.save # it should be happy at this point because profile_id should be set
d.save

Answer 2

Store the type(Nurse/Doctor) as resource for User and have a controller for User

class User
  #resource will be nurse/doctor etc
  belongs_to :resource, polymorphic: true, dependent: :destroy 
  accepts_nested_attributes_for :resource

  #add user specific validations here
end

#user will be either doctor or nurse and not both

class Doctor 
  has_one :user, as :resource 
  #add doctor specific validations
end

class Nurse
  has_one :user, as :resource
  #add nurse specific validations
end

now, when u are creating user of type doctor/nurse, u can ask the user to select the type and as per the choice render a nested form for the selected type. You can either render nested forms for both types right in the user form or add them using an ajax when user selects the type.

example form as below in haml. 'resource_fields' is an html id.

= form_for @user ...
  = #user specific fields go here
  = #show dropdown to select type and send ajax with type to render type specific form.
  - if @user.resource.nil? #if resource is not set
    #resource_fields
  - else #if resource is present
    = render 'users/doctor_form', f: f if @user.resource.is_a? Doctor
    = render 'users/nurse_form', f: f if @user.resource.is_a? Nurse

controller method to respond to ajax for type form

def get_type_form
  @user = User.new
  @user.resource = case params[:selected_type]
                           when "Doctor"
                             Doctor.new
                           when 'Nurse'
                             Nurse.new
                           end
end

and in get_form_type.js.haml

:plain
 - if @user.resource.is_a? Doctor
   $('#resource_fields').replaceWith("#{escape_javascript(render partial: 'users/doctor_form', locals: { f: nil })}");
 - if @user.resource.is_a? Nurse
   $('#resource_fields').replaceWith("#{escape_javascript(render partial: 'users/nurse_form', locals: { f: nil })}");

and partial for doctor_form will be as

 #resource_fields
 - if f.nil?
   = fields_for "user[resource_attributes]", @user.resource do |doctor|
     = render 'users/doctor_fields', :doctor: doctor
 - if f
   = f.fields_for :resource, @user.resource do |doctor|
     = render 'users/doctor_fields', doctor: doctor

and the partial for doctor_fields will be as

 = doctor.text_field :degree
 = doctor.text_field :specialization

I had a similar functionality and i implemented using the above way.