module ActiveModel::Validations::Callbacks::ClassMethods

def after_validation(*args, &block)

person.status # => true
person.valid? # => true
person.name = 'bob'
person.status # => false
person.valid? # => false
person.name = ''
person = Person.new

end
end
self.status = errors.empty?
def set_status
private

after_validation :set_status

validates_presence_of :name

attr_accessor :name, :status

include ActiveModel::Validations::Callbacks
include ActiveModel::Validations
class Person

Defines a callback that will get called right after validation. 
def after_validation(*args, &block)
  options = args.extract_options!
  options = options.dup
  options[:prepend] = true
  set_options_for_callback(options)
  set_callback(:validation, :after, *args, options, &block)
end

def before_validation(*args, &block)

person.name # => "bob"
person.valid? # => true
person.name = ' bob '
person = Person.new

end
end
name.strip!
def remove_whitespaces
private

before_validation :remove_whitespaces

validates_length_of :name, maximum: 6

attr_accessor :name

include ActiveModel::Validations::Callbacks
include ActiveModel::Validations
class Person

Defines a callback that will get called right before validation. 
def before_validation(*args, &block)
  options = args.extract_options!
  set_options_for_callback(options)
  set_callback(:validation, :before, *args, options, &block)
end

def set_options_for_callback(options) 

def set_options_for_callback(options)
  if options.key?(:on)
    options[:on] = Array(options[:on])
    options[:if] = [
      ->(o) {
        options[:on].intersect?(Array(o.validation_context))
      },
      *options[:if]
    ]
  end
end