You can mix in LifecycleCallbacks to the field and override beforeSave there, 
if you prefer. Someone correct me if I'm wrong, but I think beforeSave is 
called before it is known if save will fail. And in afterSave I don't know what 
'dirty_?' and 'was' are set to. So you may possibly want to create generic 
trait that uses beforeSave and afterSave together, so beforeSave temporarily 
stores the relevant history data but only afterSave saves the history. But 
again, I'm making a bunch of assumptions.


-------------------------------------
David Pollak<[email protected]> wrote:

MappedField.dirty_? -- was the field changed?

MappedField.is -- the current value

MappedField.was -- the value pulled from the DB

On Tue, Jan 26, 2010 at 1:37 PM, Gang <[email protected]> wrote:

> Hi all,
>
> Somebody please help on this......
>
> Before I save the Mapper object back to database, I need to check if
> one of the mapped field changed; if changed, I need trigger another
> database call(create a new entry in a history table).  What is the
> best way doing it?  Do I have to override MetaMapper's beforeSave() to
> query database for changes before save?
>
> I'm using CRUDifier and its provided "edit" page to submit user
> input.  Could somebody explain to me what is the life cycle of the
> Mapper object after user click on "Edit" button?
>
> Thanks in advance!
>
> Gang
>
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