Formtastic - custom return value for :include_blank option

Question

I'm using Formtastic (in ActiveAdmin), and I need to display a collection in a select tag for a field handled by the Ancestry gem. It's working well for the collection, but I also need a blank value in the list for clearing the field. I've tried :include_blank, but it's returning an empty string, but the validator (I can't change it, it's in the Ancestry gem) rejects it because it want nil.

How I can change the return value of :include_blank in order to return nil instead of an empty string ?

my code:

 f.input :ancestry, as: :select, collection: Category.all, :member_value => Proc.new { |c| c.path_ids.join("/") }, include_blank: true

"include_blank: true" is optional here, it's doing the same thing with or without it.

Answer 1

如果你使用f.input :parent_id而不是f.input :ancestry呢？