Programmatically copying ActiveModel validators from one model to another?

I’m writing a library that will require programmatically copying validations from one model to another, but I’m stumped on how to pull this off.

I have a model that is an ActiveModel::Model with some validation:

class User < ActiveRecord::Base

validates :name, presence: true

end

And another model that I’d like to have the same validations:

class UserForm

include ActiveModel::Model

attr_accessor :name

end

Now I’d like to give UserForm the same validations as User, and without modifying User. Copying the validators over doesn’t work, because ActiveModel::Validations hooks into callbacks during the validation check:

UserForm._validators = User._validators

UserForm.new.valid?

=> true # We wanted to see false here, but no validations

are actually running because the :validate callback

is empty.

Unfortunately, there doesn’t seem to be an easy way that I can see to programmatically give one model another’s validation callbacks and still have it work. I think my best bet is if I can ask Rails to regenerate the validation callbacks based on the validators that are present at a given moment in time.

Is that possible? If not, is there a better way to do this?

Why don’t you try creating a concern and decorate the class with that concern that contains the validations?

you can have a look here: http://stackoverflow.com/questions/11372484/rails-put-validation-in-a-module-mixin and here: http://blog.andywaite.com/2012/12/23/exploring-concerns-for-rails-4/

does this needs to be done in run time?

hope it helps.