Would nilFields work as well?

Sean

-----Original Message-----
From: squeak-dev-bounces at lists.squeakfoundation.org [mailto:squeak-dev-bounces at lists.squeakfoundation.org] On Behalf Of Igor Stasenko
Sent: Tuesday, February 19, 2008 11:37 AM
To: The general-purpose Squeak developers list
Subject: Re: [Newbies] How to empty a collection?

On 19/02/2008, goran at krampe.se <goran at krampe.se> wrote:
> Hi!
>
> Reinout Heeck <reinz at desk.org> wrote:
> > goran at krampe.se wrote:
> > > The *normal* way people usually do it thoiugh is to *not depend on 
> > > the
> > > identity* of the Collection - different objects should typically 
> > > not share the same Collection. And if you don't share - then the 
> > > easy way out is to just do:
> > >
> > >     myCollection := OrderedCollection new "or whatever class you use"
> > >
> > > ...in order to empty it.
> >
> >
> > A word of caution: identity should be preserved in the 'normal' 
> > case,
>
> I agree. While I still think relying too much on identities is a 
> dangerous practice.
>
> > replacing with another collection should be regarded as the 
> > exceptional case. Your assertion that "different objects should 
> > typically not share the same Collection." is only valid in limited cases.
>
> Well, I still stand by it as a general "nice rule". :)
>
> > I'm talking from my experience with building mvc-based apps on 
> > VisualWorks. Code needs to be decoupled, ie 'model' objects and 
> > collections should not know about the UI's that are coupled to them, 
> > this is achieved with the various dependency mechanisms available in VW.
>
> I know, I used VW back in the 2.5-3.x days and while I first thought 
> the adapter-frenzy was cool I later also started thinking it was 
> over-engineered as hell. ;)
>
> > Changing identity of the collections will break this paradigm big 
> > time (regardless of whether the dependents are managed in a global 
> > dictionary or by the collection itself).
>
> Yes, if your adapters/UI components etc cling onto the collections 
> themselves, then yes, you will be bitten big time. I still think that 
> paradigm is fishy - but again, I only presented the way people
> *typically* go about this thing - I still of course would like to 
> preserve identity and introduce #removeAll. It is better in all 
> respects.
>
> If the *intent* is to "remove all elements" - then the message should 
> state exactly that intent. Doing stuff like "aColl copy do: [:each | 
> aColl remove: each]" is just plain dumb and silly, though it would 
> probably qualify as a default implementation in class Collection. :)
>
It can be even shorter then:

Collection>>removeAll
   self removeAll: self copy

> regards, Göran
>
>


--
Best regards,
Igor Stasenko AKA sig.