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

Ruby on-RailsRubyValidationModel

Ruby on-Rails Problem Overview

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. Could someone provide an example of when I would want to use each?

For example, I have a Band model and each Band has a Genre. When I validate the presence of a genre, if the genre is missing should the error be added to the base?

The more examples the better

Thank you!

Ruby on-Rails Solutions

Solution 1 - Ruby on-Rails

It's worth noting (since this shows up in the search engines, which is how I found it) that this is deprecated. The Rails 3 way of doing it is below but is no longer valid as of Rails 7 (see the comment from April 2022)

errors[:base] << "Error message"    

the preferred way of doing it is

errors.add(:base, "Error message")

Solution 2 - Ruby on-Rails

A missing genre would be a field error. A base error would be something like an exact duplicate of an existing record, where the problem wasn't tied to any specific field but rather to the record as a whole (or at lest to some combination of fields).

Solution 3 - Ruby on-Rails

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


  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" )

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


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Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestionTonyView Question on Stackoverflow
Solution 1 - Ruby on-RailsGSPView Answer on Stackoverflow
Solution 2 - Ruby on-RailsMarkusQView Answer on Stackoverflow
Solution 3 - Ruby on-RailsJon KernView Answer on Stackoverflow