How to check a model object is persisted to DB or a new object?

category = Category.new

This isn't persi开发者_运维百科sted to DB yet, so how to distinguish form an object that is saved in the database?

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

:)

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