rails how to check an model object has persistenced to db or a new object

Question

e.g.

c=Category.new

this is didn't persistence to db, how to distinguish a object wheather persistenced to db yet

Answer 1

c.persisted?  # => true if persisted
c.new_record? # => true if not persisted

:)

Answer 2

c.new_record? # true if new, false if saved