Seeing what has changed in ActiveRecord

rubyonrails-talk
1

I have a callback (before_save) that I want to trigger only when certain fields within a record have changed. For example given a user record with 'username', 'password' and 'date_of_birth' I would like the callback to do something only when the 'username' or 'password' changes or when the 'date_of_birth' changes from nil to something real. For example, how would I write...

before_save :audit_changes

def audit_changes   if old.username != new.username     audit("The username has changed from #{old.username} to #{new.username})   end

  if old.password != new.password     audit("The user has changed their password")   end

  if old.date_of_birth == nil and new.date_of_birth != nil     audit("The user has finally set their date of birth")   end end

Now this is just a little example of what I want to do, don't get hung up on the example, but how can I write this?

2

Active Record has API for that:

    ActiveModel::Dirty

so you basically could test whether username_changed?, for example.

The examples in AM::Dirty include the module by hand, but you don't need to do that in AR models.

3

Thank you, I've been googling away like crazy but forgot to use that magic word *DIRTY*. Damn I knew it was available.

Thank you.