Ruby on Rails: errors.add_to_base vs. errors.add

Question

I have read that errors.add_to_base should be used for errors associated with the object and not a specific attribute. I am having trouble conceptualizing what this means. Cou

Answer 1

In this example, you can see field validation (team must be chosen). And you can see a class/base level validation. For example, you required at least one method of contact, a phone or an email:

class Registrant
  include MongoMapper::Document

  # Attributes ::::::::::::::::::::::::::::::::::::::::::::::::::::::
  key :name, String, :required => true
  key :email, String
  key :phone, String

  # Associations :::::::::::::::::::::::::::::::::::::::::::::::::::::
  key :team_id, ObjectId
  belongs_to :team
...
  # Validations :::::::::::::::::::::::::::::::::::::::::::::::::::::
  validate :validate_team_selection
  validate :validate_contact_method
...

  private

  def validate_contact_method
    # one or the other must be provided
    if phone.empty? and email.empty?
      errors.add_to_base("At least one form of contact must be entered: phone or email" )
    end
  end

  def validate_team_selection
    if registration_setup.require_team_at_signup
      if team_id.nil?
        errors.add(:team, "must be selected" )
      end
    end
  end
end