Rails scope that does nothing for NOT IN values

Question

I have a Rails 3 scope that excludes an array of ids.

What is the best way to write the scope so that it does nothing when the array is empty and is still chainable? I c

Answer 1

If the ids array is empty then don't return anything.

scope :excluding_ids, lambda { |ids|
  where(['id NOT IN (?)', ids]) if ids.any?
}

The query will run without any additional constraints on the query if there are no ids.