Question

Can someone explain me this behaviour of AR object:

u = User.first
uu = u.dup

uu == u  #=> true
u == uu  #=> false

Why is the latter not true?

Answer 1

This is because ActiveRecord::Base#== returns false if the second object is a new record. Since uu.new_record? is true, when doing u == uu it returns false; but u.new_record? is false, so uu == u does not fail that check.

This behavior has changed since Rails 3.0 and both u == uu and uu == u will return false in Rails 3.2 (and possibly 3.1).