Re: [Newbies] Proper object removal
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: DataManagerdeleteSelectedAbstractors 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. I assume that you want to empty the selected collection as well. you could do DataManagerdeleteSelectedAbstractors self selected copy do: [:each | self abstractors remove: each. self selected remove: each. ] regards, Norbert ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
[Newbies] Re: Proper object removal
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:
DataManagerdeleteSelectedAbstractors
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.
/Klaus
I assume that you want
to empty the selected collection as well. you could do
DataManagerdeleteSelectedAbstractors
self selected copy do: [:each |
self abstractors remove: each.
self selected remove: each.
]
regards,
Norbert
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Re: [Newbies] Re: Proper object removal
On 04.06.2008, at 10:32, Klaus D. Witzel wrote:
On Wed, 04 Jun 2008 09:55:11 +0200, Norbert Hartl wrote:
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.
Yikes. Klaus, please keep the hair-splitting to squeak-dev if possible.
Assigning to a block parameter is just wrong. Setting temps to nil is
unnecessary in any normal method. If your code actually needs to worry
about this, then you left the beginner playground.
Rob: Here's a recipe to find out what is keeping your instances from
being garbage-collected:
http://wiki.squeak.org/squeak/2631
- Bert -
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Re: [Newbies] Proper object removal
On Wed, Jun 4, 2008 at 12:45 AM, Herbert König [EMAIL PROTECTED] wrote: if you inspect this you get an inspector on an Array. To the left select any entry with a left click (on Windows) and select objects pointing to this value. You get another inspector with an array of the objects pointing to the object you can't delete. Again inspecting one of these objects you can see how it points to your original object. This might give you a clue. And manually deleting these references (setting them to nil in the inspector) will eventually free your original object for garbage collection. This is helpful...and leads me to explain a little more because I was making an assumption that might not be correct... I am writing a little arbitrary data collection application using Squeak and Aida. I can build forms with tabbed pages and add various fields, move them up and down, give them different labels, that whole thing. In short, I can create lots of objects within objects within objects. My main classes are: DataManager -- Manages a list of DataAbstractors DataAbstractor -- Manages the DynamicRecordPage(s) (basically groups of fields) DynamicRecordPage -- Manages FieldDefinition(s) DynamicRecord -- Holds the data and handles arbitrary messages based on a FieldDefinition. I have been assuming that if I get rid of a DataAbstractor, all it's underlying objects would just go away as well (Pages and Records). Do you have to explicitly remove the child objects BEFORE removing a parent object to ensure that it is removed properly? If some of the objects you find are WeakArray or such you are in the (to me) murky area of finalization and weak references. Squeak dev would be the place to ask. Fortunately, these are all recognizable objects that I would expect! You don't state the size of your problem. Is it three or is it thousands of instances hanging around?. Well, it is a few right now, but just grows continually as I use it! Nothing ever goes away, so I figure it will BE thousands if I don't figure this out. Every now and then I just save my project, blow it away, garbage collect, and reload everything. So far, that's the only way I can seem to get rid of anything! I once tried the pointer finder tool but wasn't satisfied with it. And the swiki has a page on cleaning up junk. RR I still see the object I removed, even with an explicit RR Smalltalk garbageCollect or garbageCollectMost. RR Anything I create seems to hang around forever. Sometimes saving and reloading an image does a more thorough job than garbageCollect. Maybe because of the above mentioned weak references. Thanks for your help... Rob ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Re: Proper object removal
On Wed, Jun 4, 2008 at 6:12 AM, Bert Freudenberg [EMAIL PROTECTED] wrote: Yikes. Klaus, please keep the hair-splitting to squeak-dev if possible. Assigning to a block parameter is just wrong. Setting temps to nil is unnecessary in any normal method. If your code actually needs to worry about this, then you left the beginner playground. I was hoping that was not the case! I WANT to be a beginner right now, not understanding something simple! Rob: Here's a recipe to find out what is keeping your instances from being garbage-collected: http://wiki.squeak.org/squeak/2631 Thanks, Rob ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Proper object removal
2008/6/4 Rob Rothwell [EMAIL PROTECTED]: On Wed, Jun 4, 2008 at 3:55 AM, Norbert Hartl [EMAIL PROTECTED] wrote: Hi 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. I assume that you want to empty the selected collection as well. you could do DataManagerdeleteSelectedAbstractors self selected copy do: [:each | self abstractors remove: each. self selected remove: each. ] So...why would I use a copy (self selected copy) in this case? Is that a clue to my misunderstanding? Rob because self selected do: [:each | self selected remove: each ] is to avoid ... as it iterates on the collection on wich you're removing elements... Try aColl:=#(1 2 3) asOrderedCollection. ^aColl do: [:ea | aColl remove ea ] see here: http://bugs.squeak.org/view.php?id=6937 Cédrick ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
[Newbies] Re: Proper object removal
On Wed, 04 Jun 2008 12:12:59 +0200, Bert Freudenberg wrote:
On 04.06.2008, at 10:32, Klaus D. Witzel wrote:
On Wed, 04 Jun 2008 09:55:11 +0200, Norbert Hartl wrote:
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.
Yikes. Klaus, please keep the hair-splitting to squeak-dev if possible.
Ah. Didn't know that enumerating+removing with a block with argument
+ GC'ing in the same method, belongs to hair-splitting. Instead, I always
thought that's one of the reasons that at least one to-be-removed object
is guaranteed to not go away.
But anyways, thanks for letting me know ;)
Assigning to a block parameter is just wrong.
You better read before you write (the way you most often do indeed ;) then
you'd find that I didn't write any assignment to anything. Instead, I
ignored that and pointed to a potential beginner's problem. Sorry you
didn't like that ;)
Setting temps to nil is unnecessary in any normal method. If your code
actually needs to worry about this, then you left the beginner
playground.
And if he does removal+GC+check for success in the same method? I cannot
see whether someone just copies arbitrary statements given in a response
to a question, or carefully puts them into separate methods, in his code
in his .image, now or never ;)
Rob: Here's a recipe to find out what is keeping your instances from
being garbage-collected:
http://wiki.squeak.org/squeak/2631
- Bert -
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Re: [Newbies] Re: Proper object removal
On Wed, Jun 4, 2008 at 8:41 AM, Klaus D. Witzel [EMAIL PROTECTED]
wrote:
{'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.
So...if I do line 1, then line 3, should I see items in the Array, or just
the Array itself.
This is all very interesting, because in my application I am creating lots
of collections of objects maintaining parent/child pointers, and I have
obviously just done it WRONG!
Chasing pointers and objects is showing me that when I remove objects from
my collections, I need to do that all the way down, I think...
Thank you for helping my brain move in the right direction.
Rob
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[Newbies] Re: Proper object removal
On Wed, 04 Jun 2008 15:20:05 +0200, Rob Rothwell wrote:
On Wed, Jun 4, 2008 at 8:41 AM, Klaus D. Witzel wrote:
{'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.
So...if I do line 1, then line 3, should I see items in the Array, or
just the Array itself.
What you want to see (according to your question about object removal) is
just the empty array; and what I wanted to point out (without
hair-splitting ;) is, that when you GC+check this within the same method,
it *must* fail.
In Smalltalk it's very easy to script the removal+GC+check, for example in
a workspace or add GC+check temporarily in a debugger session; that was my
concern.
This is all very interesting, because in my application I am creating
lots
of collections of objects maintaining parent/child pointers, and I have
obviously just done it WRONG!
A good example for maintaining parent/child objects, which works
perfectly, is Smalltalk's #addSubclass: #removeSubclass: (both on the
instance side of Class); when you check these two methods think that
'superclass' is your parent pointer.
Chasing pointers and objects is showing me that when I remove objects
from
my collections, I need to do that all the way down, I think...
Thank you for helping my brain move in the right direction.
Rob
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Re: [Newbies] Re: Proper object removal
On Wed, Jun 4, 2008 at 9:41 AM, Klaus D. Witzel [EMAIL PROTECTED] wrote: What you want to see (according to your question about object removal) is just the empty array; and what I wanted to point out (without hair-splitting ;) is, that when you GC+check this within the same method, it *must* fail. I guess it would have to, wouldn't it? In Smalltalk it's very easy to script the removal+GC+check, for example in a workspace or add GC+check temporarily in a debugger session; that was my concern. A good example for maintaining parent/child objects, which works perfectly, is Smalltalk's #addSubclass: #removeSubclass: (both on the instance side of Class); when you check these two methods think that 'superclass' is your parent pointer. Thanks for pointing this out--maybe I can learn something and get this working properly! Rob ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Re: Proper object removal
On 04.06.2008, at 15:20, Rob Rothwell wrote:
On Wed, Jun 4, 2008 at 8:41 AM, Klaus D. Witzel [EMAIL PROTECTED]
wrote:
{'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.
So...if I do line 1, then line 3, should I see items in the Array,
or just the Array itself.
This is all very interesting, because in my application I am
creating lots of collections of objects maintaining parent/child
pointers, and I have obviously just done it WRONG!
Chasing pointers and objects is showing me that when I remove
objects from my collections, I need to do that all the way down, I
think...
Normally you do not need to do this all the way down. Say you have a
tree of objects, where the parent points to its children, and the
children each back to its parent. Then it is sufficient to remove one
child to have the whole subtree rooted at the child go away. There is
no need to delete all the children's children. Also, the back
pointers do no harm. But it is important that there are no other
references to these objects - no inspectors, debuggers, etc.
As soon as there is no path from a global object to your object, it
is subject to garbage collection (which will happen later, not
immediately). The #allInstances method still finds these unreachable
objects, because it simply looks at each and every object that was not
yet gc'ed.
- Bert -
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Re: [Newbies] Proper object removal
Rob Rothwell-2 wrote: [snip] DataManagerdeleteSelectedAbstractors self selected copy do: [:each | self abstractors remove: each. self selected remove: each. ] So...why would I use a copy (self selected copy) in this case? Is that a clue to my misunderstanding? Because the copy of the collection will live only during the execution of #do: and thus it won't hang on to references to your objects. Saludos, Victor Rodriguez. Rob ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners -- View this message in context: http://www.nabble.com/Proper-object-removal-tp17638745p17645408.html Sent from the Squeak - Beginners mailing list archive at Nabble.com. ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
[Newbies] underscore / left-arrow query
hello, when i first started using squeak a couple of years ago, the assignment operator was displayed as a left arrow, which i really like. it looks very clean to my eyes (better to me than the pascal like := syntax). in my current image, a seaside 2.8-530 image, in workspaces etc, i don't get my lovely left arrow when I assign variables; just a regular underscore. is it now considered bad form to use the left arrow, or can I set this in preferences somewhere such that my underscore is converted to an exciting left-arrow? if it's bad form or broken, i'll mend my ways. I tried to search for preference settings, but without joy. Google had an unreasonably high noise ratio as well. thanks. Kel. ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
[Newbies] Ubuntu and Squeak
Ok...so we sort of got Ubuntu running on a server...which VM should I go get? (Yes, I am so NOT Linux-enabled at this particular time...) Thanks! Rob ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Ubuntu and Squeak
On Thu, Jun 5, 2008 at 10:07 AM, Rob Rothwell [EMAIL PROTECTED] wrote: Ok...so we sort of got Ubuntu running on a server...which VM should I go get? (Yes, I am so NOT Linux-enabled at this particular time...) Hi Rob. It depends on your architecture. If you're just running on 32-bit x86, you can just use the latest Linux VM from http://www.squeak.org/Download. Here's a direct link, because I'm such a nice guy and my browser is open on it anyway: http://ftp.squeak.org/3.10/unix-linux/Squeak-3.10-1.i686-pc-linux-gnu.tar.gz IIRC there may be a VM that is installable from Ubuntu's package manager. That would work as well. If you installed the AMD64 bit version of Ubuntu, then things are a bit trickier. Then you'll need to look at http://www.squeakvm.org/. Gulik. -- http://people.squeakfoundation.org/person/mikevdg http://gulik.pbwiki.com/ ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
