Awesome simple solution for Rails ActiveRecord dirty tracking associations

dirty_associations.rb

# Credit Brandon Weiss of http://anti-pattern.com/dirty-associations-with-activerecord

# app/models/dirty_associations.rb
module DirtyAssociations
  attr_accessor :dirty
  attr_accessor :_record_changes

  def make_dirty(record)
    self.dirty = true
    self._record_changes = record
  end

  def changed?
    dirty || super
  end
end

# app/models/lolrus.rb
class Lolrus
  include DirtyAssociations

  has_many :buckets,
           :after_add    => :make_dirty,
           :after_remove => :make_dirty
end

# Usage
lol = Lolrus.create!
lol.buckets << Bucket.new
lol.changed? 
# => true

lol._record_changes
# => #<Bucket# ... >

lol._record_changes.changed?
# => true

lol._record_changes.changes?
# for example ...
# => {[attr] => [old_value, new_value]}

Neat!

When adding or removing multiple records only the last one would be present in _record_changes.

You could rewrite made_dirty to get all changed records like so:

def make_dirty(record)
  self.dirty = true
  self._record_changes ||= []
  self._record_changes << record
end

Also, reload doesn't reset the _record_changes. You can overload the reload method like so:

def reload(*)
  super.tap do
    self._record_changes = nil
  end
end

@yourivdlans hi. thanks for you solution. He does not mentioned any reload methods. Can you elaborate why we need reload?