Ancestry: skip element from scope

Question

Using gem ancestry.

How skip self element from Category::ActiveRecordRelation or need use scope?

= simple_form_for @category do |f|
  = f.input :parent_id, collection: Category.roots 

Something like:

= f.input :parent_id, collection: Category.roots.except(@category)

Answer 1

= f.input :parent_id, collection: Category.roots.where("id <> ?", @category.id)

or via a scope

category.rb

scope :except, lambda{ |category| where("id <> ?", category.id) }

then

= f.input :parent_id, collection: Category.roots.except(@category)