Fixes validations with validates_uniqueness_of

[artplan1]

Hi, we're having issues with uniqueness validations done with validates_uniqueness_of.
I assume that constant in validates_uniqueness_of is still points to default rails validator.

    Failure/Error: model_class.create(attribute1 => "foo")

     ActiveRecord::StatementInvalid:
       PG::UndefinedColumn: ERROR:  column container_posts.title does not exist
       LINE 1: SELECT 1 AS one FROM "container_posts" WHERE "container_post...

I came up with straightforward solution, but I believe there are better solutions.

[shioyama]

Thanks for the PR! ❤️

I came up with straightforward solution, but I believe there are better solutions.

Hmm well I think it's fairly safe to do it this way, since this only overrides the method on the class and not other classes.

For reference, the reason the code has const_get/const_set is because validates looks for the constant UniquenessValidator and will prefer the model namespace if there is a constant defined there:

https://github.com/shioyama/rails/blob/5262ec59002e461b2fdb8cb81f0ac1623b1cd2fd/activemodel/lib/active_model/validations/validates.rb#L119

            validator = key.include?("::") ? key.constantize : const_get(key)

So by defining the constant, we can selectively override the default uniqueness validator on this model only. If that wasn't possible we'd have to override validates which would be much more tricky.

But validates_uniqueness_of can easily be overridden on the model since it's just a one-line method. So I think this is a 👍 solution.

[shioyama]

Thanks for the test!

[shioyama]

LGTM 👍