Rails - Nov 2009 - How can I make an aggregated property support ActiveRecord::Dirty semantics?

Hoping one of the many experts here might help out a newb...

I have an aggregated attribute which I want to be able ask about its _changed?
ness, etc.

composed_of :range,
 :class_name => ''Range'',
 :mapping => [ %w(range_begin begin), %w(range_end end)],
 :allow_nil => true

If I use the aggregation:

foo.range = 1..10

This is what I get:

foo.range          # => 1..10
foo.range_changed? # NoMethodError
foo.range_was      # ditto
foo.changed        # [''range_begin'',
''range_end'']

So basically, I''m not getting ActiveRecord::Dirty semantics on
aggregated attributes (they are on the underlying db attrs).

Is there a beautiful way to implement dirty semantics on the aggregation?
I''m not having a lot of luck with alias_attribute_with_dirty, etc.  I
really am unfond of making my own range_changed?, range_was, etc.  Frankly, I
was a bit surprised that aggregation didn''t support dirty natively...

Advice greatly appreciated.

On Nov 6, 12:51 pm, Eric Hahn
<e...-StdO6VYKx2VBDgjK7y7TUQ@public.gmane.org>
wrote:
> So basically, I''m not getting ActiveRecord::Dirty semantics on
aggregated attributes (they are on the underlying db attrs).
>
> Is there a beautiful way to implement dirty semantics on the aggregation?
I''m not having a lot of luck with alias_attribute_with_dirty, etc.  I
really am unfond of making my own range_changed?, range_was, etc.  Frankly, I
was a bit surprised that aggregation didn''t support dirty natively...
The dirty stuff is all centred around actual attributes. you could
define

def range_changed?
  range_begin_changed? || range_end_changed
end

def range_was
  range_begin .. range_end
end

and so on. shouldn''t be too hard to automate definition of these
methods.

Fred
>
> Advice greatly appreciated.