Re: Action based undo or snapshot based undo?

FROM : Greg Titus
DATE : Wed Jan 29 21:03:50 2003

Oh good, then I completely second Bill's recommendation, then. I just
haven't read his book, so I took Alex's word for what it says...

- Greg

On Wednesday, January 29, 2003, at 11:07  AM, Jim Correia wrote:

> On Wednesday, January 29, 2003, at 12:37  PM, Greg Titus wrote:
>

>> On Tuesday, January 28, 2003, at 11:32  PM, Alexander Lamb wrote:
>>

>>> As I understood, the NSUndoManager is based on the idea of recording
>>> a series of actions needed if the user wants to undo what he just >>
>>> did.
>>> In Bill Cheeseman's book, he recommands recording those actions in
>>> the action methods rather than at the object level, because it
>>> reflects more closely what the user is doing and allows to customize
>>> the undo for an action that may involve several changes on objects
>>> attributes.

>>
>> I totally disagree with Bill here (sorry Bill), and I think that that
>> is why you are running into problems.
>>
>> You should register the changes at the object level, but you should
>> set the action name in the action methods.

>
> I've read Bill's book, but don't have it handy to verify this. It is
> my recollection that he recommends exactly what you do Greg - undo at
> the model level and set the action name in the action methods.
>
> You can grab the sample code for the book here
>
>     <http://www.stepwise.com/articles/VermontRecipes/>
>
> which implements undo in that manner.

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