combine results from two queries and order by created_at? [rails 3]

Question

Looking for a simple method utilizing active record to grab data from two models, combine the data, and then sort the combined output by created_at.

For example:

Answer 1

How about something like (untested):

class User < ActiveRecord::Base
  scope :activities_by_date, :joins(:comments).joins(:likes).order("created_at desc")
end

Then you can do @user.activities_by_date and let the db do all the work

Answer 2

I believe it should be as simple as:

combined_sorted = (User.comments + User.likes).sort{|a,b| a.created_at <=> b.created_at }