How to exclude an array of ids from query in Rails (using ActiveRecord)?

Rails 4 solution:

ids_to_exclude = [1,2,3]
array_without_excluded_ids = Item.where.not(id: ids_to_exclude)

This should work:

ids_to_exclude = [1,2,3]
items_table = Arel::Table.new(:items)

array_without_excluded_ids = Item.where(items_table[:id].not_in ids_to_exclude)

And it's fully object-oriented with no strings :-)