bulk_validator.rb

class BulkValidator
  attr_accessor :items, :bulk_validations
  
  def initialize(items, validations)
    @items = items
    @bulk_validations = build_bulk_validations(validations) 
  end
  
  def candidates
    bulk_validations.each do |validation|
      @items = validation.apply items
    end
    items
  end
  
  def invalidate_candidates
    
  end
      
  private
  
  def build_bulk_validations(validations)
    validations.map do |validation|
      case validation.validation_type
      when "presence" then PresenceValidation.new(validation.options)
      ...
      else
        fail("Unknown validation type #{validation.validation_type}")
      end
    end
  end

catalog_field.rb

class CatalogField < ActiveRecord::Base
  
  ...
  
  # Бывшая dirty_validated_items
  def invalidated_items
    bulk_validator = BulkValidator.new(items, validations)
    bulk_validator.candidates
  end
  
  ...
  
end

catalog_fields_controller.rb

def confirm_changes
  @catalog_field.assign_attributes(catalog_field_params)
  @items = @catalog_field.invalidated_items
  
  # Вообще проверь почему здесь следующая строчка присутствует :)
  render :edit unless @catalog_field.valid?
end