Alex,
About weak reference listeners - what kind of listeners are created when
bindings are defined in MXML? Like dataProvider="{myAc}"? And would it
help to use [Bindable] myColl:ICollectionView as the source? I hear you
on trying to make things like this easy. I think the ViewStack loading
Modules conditionally is a pretty common scenario for app development.
One of the things I am seeing is that it easier to get the module to
unload if it isn't the currently selectedChild of the ViewStack, but so
far I get the best results when a brand new module is loaded before
exiting the application. Then the other module becomes relatively easy
to gc.
In my app, one of the modules manages a particular product type. Based
upon search criteria, a datagrid will be populated. If they want to
edit a given dg item, there's a popup editor which makes a copy of the
editable object and binds that to a form. The user makes edits and
chooses to save or not the item. Right now, that's what I'm focusing
on, because the editable copy I make seems to be hanging around in
memory after attempting to unload the module and might be contributing
to the problem.
Jeff
-----Original Message-----
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Alex Harui
Sent: Monday, April 27, 2009 6:15 PM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules - Binding is the
Enemy?
I haven't looked at ModelLocator, but in general, if you have a
single instance of something and are binding to it from a module, code
in the module will add a listener to the single instance. This creates
a reference from the single instance to the module, but Binding should
be using a weak reference listener. Maybe it is time for me to build a
test case and look. We want to make this kind of thing "easy". If
ModelLocator keeps its own list of subscribers, that could be a problem.
If your local models are listening for changes to the central model and
not using weak reference listeners that will also be a problem.
If the PopUp is being gc'd then that should no longer pin the
module. I haven't looked at many popup scenarios so there could be
something there. In general though, I've found the profiler will
eventually tell me the answer. I assume you know that new classes pin
modules if they bring in new Style definitions that get registerd with
the StyleManager.
That said, the Flash Player will not always gc() everything it
could in one pass, and sometimes does hang onto things a bit longer, so
the load/interact/unload/checkmemory test will not always succeed. If
loading the module again or loading a different module eventually causes
the release of the first module, we consider that "success". Another
test we run is an overnight test of loading and unloading modules that
are published for release mode (no debug info) and run on the release
player instead of the debugger player. Memory should stabilize after a
while. The debugger player has a reputation for hanging on to things
that the release player won't because it is handling debug info in the
debug SWFs.
Alex Harui
Flex SDK Developer
Adobe Systems Inc. <http://www.adobe.com/>
Blog: http://blogs.adobe.com/aharui
<http://blogs.adobe.com/aharui>
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Battershall, Jeff
Sent: Monday, April 27, 2009 11:36 AM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules - Binding is the
Enemy?
Thanks Alex, very much. The main app is only handling
login/logout duties and the event-command-delegate classes to do so. I
moved away from ModelLocator in the concern that it, being a singleton,
may be keeping a reference to UI objects that are using ModelLocator
objects as dataProviders and thus prevent a clean unload. After all, by
definition, a singleton is going to persist after a module is unloaded,
true? Maybe I was wrong about that, but I'll tell you, I was trying
everything to get that module to unload. Everyone was a suspect. Bear
with me while I try to get my wits around this stuff. What I'm doing
how is keeping all my models local to the module that uses them and
injecting data via command and delegate classes. This seems to work ok.
As far as PopUps, I'm calling removePopUp() and also removing
listeners to custom events I've defined in the popup.
I'm also seeing some behavior where the module will remain in
memory after unloading (as reported by the profiler) until I create a
new instance of that particular module class and populate the
dataProvider of one of its children. The holy grail of a 100% clean
module load/unload has not been attained, but I believe I'm getting
closer.
Jeff
-----Original Message-----
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Alex Harui
Sent: Monday, April 27, 2009 1:39 PM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules - Binding is the
Enemy?
Every time I've debugged a suspected Binding leak, I've
found that it sets up weak references in the right places and the
problem was always somewhere else. However, I wouldn't bet against
there being a scenario out there that does leak. We're looking at other
module unloading scenarios right now so I'd still be willing to look at
a simple test case.
IMHO, the main app should "never" reference the model.
If you have a model Singleton, the module can bind to the singleton.
IMHO, that's a better model/view design anyway. I would expect all
popups related to the module to be removed in order for the module to
unload.
One aspect of the modules design is that it does not
require an unload() command. The design was that you would load a
module and generate an instance (or several) of the module's classes and
once you've cleaned up all references to those instances, the module
would go away in a future gc pass. That way, you wouldn't have to track
instances and know when it is time to call unload(). In order to
implement such a design, the module SWF is given an unload() call right
away so that its generated instances are supposedly the only remaining
references to the modules classes thus preventing garbage-collection.
Given the current design, I don't think we can ever substitute
unloadAndStop() for that unload call. Also, no testing has been done by
the Flex team as to what impact unloadAndStop will have in ActionScript
if references to objects suddenly become invalid. IMHO, unloadAndStop
should only be used when there are well-defined boundaries such as
around a sub-application since sub-apps tend to be more self-sufficient.
Modules are much more tightly integrated with the main application.
However, Modules or no Modules, we realize that
debugging memory leaks is hard work. The Gumbo profiler has a new
backreference display that eliminates most extraneous backreferences,
and we welcome any other ideas for tools and techniques for finding
leaks.
Alex Harui
Flex SDK Developer
Adobe Systems Inc. <http://www.adobe.com/>
Blog: http://blogs.adobe.com/aharui
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Battershall, Jeff
Sent: Monday, April 27, 2009 6:43 AM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules - Binding is
the Enemy?
Alex, I was using 3.2 - an oversight on my part - I
upgraded to 3.3 and it does seem to help but I'm also calling
focusManager.deactivate() as well. Since that, the combobox isn't an
issue.
However there any number of different things I was doing
that were causing problems - like binding myModule.currentState to a
model. One of the challenges is injecting model data into the module
that doesn't create a refererence to the module anywhere. PopUpManager
seems to be problematic if the popup contains strong refereneces to the
module or its associated model.
I am making progress and what I'm hoping for in the end
is a definitive set of best practices concerning the use of modules.
Hopefully some of these issues might be made easier with somehting like
loader.unloadAndStop() but for modules.
Jeff
-----Original Message-----
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Alex Harui
Sent: Friday, April 24, 2009 5:43 PM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules -
Binding is the Enemy?
Jeff, which version of Flex are you using? Can
you make a test case in two 20-line mxml files?
Alex Harui
Flex SDK Developer
Adobe Systems Inc. <http://www.adobe.com/>
Blog: http://blogs.adobe.com/aharui
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Battershall, Jeff
Sent: Friday, April 24, 2009 11:57 AM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules -
Binding is the Enemy?
Gregor,
It does seem to be connected to the ComboBox
issue - is this in the Adobe BugBase? It doesn't turn up in my searches.
I can get the reference to release if I navigate to another module and
then logout, but if I change the selected index of the combo box to
greater than -1 before that, it will not release no matter what I do.
This is a royal PITA because my instantiation
code is based upon a first time load of the module and if I cannot
unload a module then my method of injecting model objects into my module
will have to be re-done. If there's no workaround for this bug, then
Modules are effectively broken if something as commonplace as a combobox
prevents an unload.
Jeff
-----Original Message-----
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Battershall, Jeff
Sent: Thursday, April 23, 2009 10:13 AM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading Modules -
Binding is the Enemy?
Gregor,
Very interesting indeed. If I login,
load the module, interact with the combobox, logout, the instance
remains in the profiler. However if I do all that and THEN load another
module and logout, the number of instances of the first module goes to
zero. These modules are being loaded into a ViewStack, BTW.
Is this the FocusManager bug you
described? Is there a workaround?
I'd be thrilled to discover that Binding
was not the culprit here.
Jeff
-----Original Message-----
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Gregor Kiddie
Sent: Thursday, April 23, 2009 9:40 AM
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading
Modules - Binding is the Enemy?
It does sound like you are describing
the bug where the focus manager holds onto the reference of the combo
box and stops the module unloading...
If you lose the combobox focus, does the
module unload?
Gk.
Gregor Kiddie
Senior Developer
INPS
Tel: 01382 564343
Registered address: The Bread Factory,
1a Broughton Street, London SW8 3QJ
Registered Number: 1788577
Registered in the UK
Visit our Internet Web site at
www.inps.co.uk <blocked::http://www.inps.co.uk/>
The information in this internet email
is confidential and is intended solely for the addressee. Access,
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Any views or opinions presented are solely those of the author and do
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________________________________
From: flexcoders@yahoogroups.com
[mailto:flexcod...@yahoogroups.com] On Behalf Of Battershall, Jeff
Sent: 23 April 2009 14:32
To: flexcoders@yahoogroups.com
Subject: RE: [flexcoders] Unloading
Modules - Binding is the Enemy?
Thanks Pedro,
I've seen what your describing in the
docs - I'm looking at this via the profiler which is giving me feedback
as to number of live instances, etc.
Here's what I'm basing my statements
on:.
1) I start up my app, which loads
modules at runtime based upon user choice from a menu.
2) Module exectues Cairngorm
Event/Command/Delegate to get array to populate a combo box. I'm passing
a reference to the module's model in my Cairngorm event and the model is
updated upon completion of the Command.
3) Combobox is bound (via MXML) to the
model.
4) If I don't interact with the
combobox, I can then logout and unload the module successfully. The
profiler tells me there was previously 1 instance of the module and now
there are zero instances.
5) If I make the combobox active (by
interacting with it in any way), and then logout, the module remains in
memory, with the profiler reporting one instance instead of zero.
6) If I then login again, the Profiler
reports 2 active instances of the module. Note that any model objects
are duplicated as well. For example, if my list of suppliers (used to
popuate my combobox) (a strongly typed AS class) was previously 64, the
profiler now reports there are 128 instances.
There's my behavior. When my UI object
(in this case ComboBox), becomes active, the binding becomes active and
then the module will not unload, even if I set the modules model to null
before attempting to unload. It would appear that I need to invalidate
all outstanding bindings to any data object before the module will fully
unload. This would seem to indicate that MXML binding (via curly
braces) isn't going to allow this.
Jeff
