Rails: calling standard validations from a custom validator

Question

Is there a way to call standard Rails validators from within a custom validator?

I have a combination of OAuth/email signup/sign in and I want to be able to call certain validators on each method of authentication. For instance, I want to be able to call validates_uniqueness_of :email if the user signs up through email and then call a single validator, for instance validates_with UserValidator.

If there isn't a way to do this I'm just going to use state tracking and a series of :if validations.

Mike Szyndel · Accepted Answer · 2013-12-29 15:30:05Z

1

I believe there's no way to call other validators from custom one, this also may possibly cause circular dependency which is dangerous.

You have to go with conditional validations, but keep in mind that you can scope them like this (taken from Rails Guides)

with_options if: :is_admin? do |admin|
  admin.validates :password, length: { minimum: 10 }
  admin.validates :email, presence: true
end

answered Dec 29, 2013 at 15:30

Mike Szyndel

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Kyle Snow Schwartz · Accepted Answer · 2018-07-24 03:17:18Z

If your goal is to call some combination of custom and standard rails validators you can do that with the validates method provided by ActiveModel::Validations

For example, you've created a custom Email Validator:

class EmailValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    record.errors.add attribute, (options[:message] || "is not an email") unless
      value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
  end
end

And you want to include it in your Person class. You can do like so:

class Person < ApplicationRecord
  attr_accessor :email

  validates :email, presence: true, email: true
end

which will call your custom validator, and the PresenceValidator. All examples here are taken from the docs ActiveModel::Validations::Validates

pcothenet · Accepted Answer · 2021-10-28 00:45:20Z

I'm not sure if this a recent change in Rails but in 6.1 it is possible to call the standard validators from a custom validator:

class VintageYearValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    ActiveModel::Validations::NumericalityValidator.new({
      attributes: attributes,
      only_integer: true,
      greater_thank_or_equal_to: 1900,
      less_than_or_equal_to: 2100
    }).validate_each(record, attribute, value)

    # Your custom validation
    errors.add() unless bla?

  end
end

Those standard Validators are not really documented (https://apidock.com/rails/v6.1.3.1/ActiveModel/Validations/NumericalityValidator) so use at your own risk. But there doesn't seem to be a risk of circular dependency. Both your custom validator and the standard Validator inherit from EachValidator.

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