validator

y.rb

require 'active_support'
require 'active_model'

class Form
  include ActiveModel::Validations
  include ActiveModel::Attributes

  attribute :blah
  validates :blah, numericality: true
end

f = Form.new
f.blah = 'a'

f.valid? # => false
f._validators[:blah].object_id # => 47297490130120

f2 = Form.new
f2._validators[:blah].object_id # => 47297490130120

Form._validators[:blah].object_id # => 47297490130120