How To: Override Build Resource({}) - Devise Wiki

add following file app/lib/devise_registrations_controller_decorator.rb

  module DeviseRegistrationsControllerDecorator
    extend ActiveSupport::Concern

    included do
      alias :devise_new :new
      def new; custom_new; end
    end
    
    def custom_new
      build_resource({}) # Custom call what you want
      respond_with self.resource
    end
  end

  Devise::RegistrationsController.send(:include, DeviseRegistrationsControllerDecorator)

add line into config/environments/development.rb

  config.to_prepare do
    Devise::RegistrationsController.send(:include, DeviseRegistrationsControllerDecorator)
  end

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