[Newbies] Re: Proper object removal

[Norbert Hartl]

On Wed, 2008-06-04 at 10:32 +0200, Klaus D. Witzel wrote:
> On Wed, 04 Jun 2008 09:55:11 +0200, Norbert Hartl wrote:
> 
> > On Wed, 2008-06-04 at 00:04 -0400, Rob Rothwell wrote:
> >> Hello,
> >>
> >> After much help already, I think I need some training in proper object
> >> removal.
> >>
> >> When my application creates an object and stores it in an
> >> OrderedCollection, and than wants to delete it, I am trying to do so
> >> quite explicitly with something like:
> >>
> >> DataManager>>deleteSelectedAbstractors
> >>     self selected do: [:each |
> >>         self abstractors remove: each.
> >>         each := nil.
> >>     ]
> >>
> >> which removes the object from my application (it's collection), and
> >> yet when I look for my object in the system with
> >>
> >
> >> DataAbstractor allInstances.
> >>
> >> I still see the object I removed, even with an explicit Smalltalk
> >> garbageCollect or garbageCollectMost.  Anything I create just seems to
> >> hang around forever.
> >>
> >> Any help understanding what I need to do to make sure my objects
> >> really go away when I am done with them would be greatly appreciated!
> >
> > The objects are still referenced in the collection you get
> > from self selected. The line with "each := nil" is useless
> > as each is only a temporary variable.
> 
> Not 100% useless, since temporary variables (and arguments, for that  
> matter) survive any attempt, from within the same method, to garbage  
> collect them:
> 
> {'this ', 'and ', 'that'} collect: [:each | ].
> Smalltalk garbageCollect.
> {thisContext tempAt: 1} inspect
> 
> first line: create some object and make a temp var point to it.
> second line: invoke GC.
> third line: see what's still pointed to by the temp var.
> 
Ok, you confused me completely. I was baffled getting a bytestring
containing 'this and that'. Shortly after I recognized the commata
in your Array assignment. I think you meant 

{'this'. 'and'. 'that}

Isn't this an issue of BlockContext? Through a similar effect I used
to learn fixTemps. Would this be the same behaviour using full closures?

Norbert

> /Klaus
> 
> > I assume that you want
> > to empty the selected collection as well. you could do
> >
> > DataManager>>deleteSelectedAbstractors
> >    self selected copy do: [:each |
> >    self abstractors remove: each.
> >    self selected remove: each.
> > ]
> >
> > regards,
> >
> > Norbert
> 
> 
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