Where should I put the Custom Validators in Rails 5?

My validator did not loaded automatically. At least is not showing when I type in the console:

> ActiveSupport::Dependencies.autoload_paths

So, I put in my config/application.rb, this line:

config.autoload_paths += %W["#{config.root}/lib/validators/"]

Rails 6

app/models/validators/ is also a sensible directory to house validators.

I choose this directory over others such as app/validators since the validators are context-specific to ActiveModel

app/models/person.rb

class Person < ApplicationRecord
  validates_with PersonValidator
end

app/models/validators/person_validator.rb

class PersonValidator < ActiveModel::Validator
  def validate(record)
    record.errors.add(:name, 'is required') unless record.name
  end
end

config/application.rb

module ...
  class Application < Rails::Application
    config.load_defaults 6.1

    config.autoload_paths += Dir[File.join(Rails.root, 'app', 'models', 'validators')]
  end
end

Specs for the validators would be placed in spec/models/validators/

I put them in /app/validators/email_validator.rb and the validator will be loaded automatically.

Also, I don't know if it's your case but you should replace this in your form. If so, a first validation is made before the user reach your controller.

  <div class="field">
    <%= f.label :email %>
    <%= f.text_field :email, required: true %>
  </div>

By :

  <div class="field">
    <%= f.label :email %>
    <%= f.email_field :email, required: true %>
  </div>