Rails render flash error message from child model-CodePudding

I've got Rails 5 monolith app where inside the registration form Doctor/Admin can create a Registrant (as a Caregiver) with linked Patient (new object CaregiverPatient represents that).

  def create
    @registrant = Registrant.new(registrant_params)
    @patient = Registrant.find(session[:patient_id_to_add_caregiver]) if session[:patient_id_to_add_caregiver]
    if @registrant.save
      # other objects that must be created (...)
      CaregiverPatient.create!(patient: @patient, caregiver: @registrant, linked_by: current_login.user.id, link_description: 0) if @patient.present?
      redirect_to registrant_path(@registrant), notice: 'Registrant Added'
    else
      build_registrant_associations
      render :new, { errors: errors.full_message }
    end
  end

Caregiver can have only one linked Patient. How to display error message from CaregiverPatient validation and prevent the @registrant from being saved if such an error occurs?

With this code I'm getting an error:

ActiveRecord::RecordInvalid in RegistrantsController#create Validation failed: Caregiver cannot be assigned a caregiver

Which is because of create! I guess but how to handle this to display flash message inside the form?

CodePudding user response：

You can use the transaction: https://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html

This allows you to handle exceptions from both create! and save! and prevent @registrant from being saved.

I consider your code should looks something like

def create
  @registrant = Registrant.new(registrant_params)
  @patient = Registrant.find(session[:patient_id_to_add_caregiver]) if session[:patient_id_to_add_caregiver]

  begin
      ActiveRecord::Base.transaction do
          @registrant.save!
          #other objects creation
          CaregiverPatient.create!(patient: @patient, caregiver: @registrant, linked_by: current_login.user.id, link_description: 0) if @patient.present?
          redirect_to registrant_path(@registrant), notice: 'Registrant Added'
      end
  rescue ActiveRecord::RecordInvalid => exception
      build_registrant_associations
      render :new, { errors: exception.message }
  end
end