rails+mongoid validate dynamic attribute

Question

I am using rails 4 + mongoid 4 beta1.

Product belongs to Category and has dynamic attributes based on category. I validate dynamic attributes with custom method, but its looks ugly. How can i use standart validate methods inside my custom method or there is a better way?

Here is my model(not full):

class Product
  include Mongoid::Document
  include Mongoid::Attributes::Dynamic

  belongs_to :category

  before_validation :custom_field_to_datatype

  validates :category_id, :presence => true
  validate :custom_fields_validator

  private
    def custom_field_to_datatype
      self.category.product_attributes.each do |pr_at|
        name = pr_at.name.to_sym
        if pr_at.type == 'boolean'
          self[name] = self[name].to_bool
        elsif pr_at.type == 'integer'
          self[name] = self[name].to_i
        end
      end
    end

    def custom_fields_validator
      max_length = 30
      max_integer = 9223372036854775807
      min_integer = -9223372036854775807

      self.category.product_attributes.each do |pr_at|
        name = pr_at.name.to_sym

        case pr_at.type
        when 'string'
          errors.add(name, "Длина строки должна быть не больше #{max_length} символов") if self[name].length > max_length
        when 'integer'
          if self[name] > max_integer
            errors.add(name, "Значение должно быть не больше #{max_integer}")
          elsif self[name] < min_integer
            errors.add(name, "Значение должно быть не меньше #{min_integer}")
          end
        end
      end
    end

end

Answer 1

Personally, I think you should move custom validators out of your model and into its own validator class. You should read this guide, especially the part about custom validator: http://edgeguides.rubyonrails.org/active_record_validations.html#custom-validators

P.s. What you are doing is not wrong though, but it is usually better to extract complex behaviour with only one responsibility, in this case validating product attributes, into its own class. Custom validators are also great for keeping your code dry, because you can use them in any class you like.