Retrieving array of ids in Mongoid

Question

how do you retrieve an array of IDs in Mongoid?

arr=[\"id1\",\"id2\"]
User.where(:id=>arr)

You can do this eas

Answer 1

Remember that the ID is stored as :_id and not :id . There is an id helper method, but when you do queries, you should use :_id:

User.where(:_id.in => arr)

Often I find it useful to get a list of ids to do complex queries, so I do something like:

user_ids = User.only(:_id).where(:foo => :bar).distinct(:_id)
Post.where(:user_id.in => user_ids)