write_attribute functionality for related objects?

rubyonrails-talk
1

Hi. Given:

class Group < AR   has_many :users end

Is it in any way possible to retain reference to the old users when they get replaced using group.users=(new_users) ?

The below doesn't work but illustrates what I'm looking for:

class Group < AR   has_many :users   def users=(new_users)     @old_users = users     write_attribute('users', new_users)   end end

I need to examine the differences when related objects (in this case users) change.

Morten

2

The below doesn't work but illustrates what I'm looking for:

class Group < AR   has_many :users   def users=(new_users)     @old_users = users     write_attribute('users', new_users)   end end

I'm currently doing something like this:

class Group < AR   has_many :users   def validate_on_update     old_users = Group.find(id).users     #Do the checks here..   end end

But that's nasty. Anyone know if there's a plugin that allows AR to contain a version of the object in the state it had as it got read from the DB for later comparison?