Global object instances get reset?

[onnodb]

Hi all,

Currently, I'm working on an Access XP database app that uses two
global objects in its code. These two objects are instances of
"controller classes". For example, one of them manages the multiple
open instances of a form (some sort of 'window manager').

These global objects are created in a module "General", by defining
them with e.g.:

Dim VwMng As New KViewManager

Now there seems to be a bit of a problem with these global objects:
when I'm running the application, at random times Access crashes when
the code accesses these global objects. Apparently, the instances are
sometimes reset by Access --- even though I'm not working on the code
and haven't recompiled anything explicitly.

I also tried modifying the above code with...

Dim VwMng as KViewManager

....and then explicitly doing a "Set VwMng = New KViewManager" in the
AutoExec startup function. Same problem: completely at random, the
references seem to become invalid.

It seems that I've just taken Access too far, or made things overly
complicated or so... So now I'm working to rework the code, but this
global objects problem keeps popping up --- e.g. defining an instance
of the class Collection in a module results in the same problem:
sometimes the collection just vanishes into thin air, crashing Access.

Now I'm sure that there are people in here with a lot more experience
than I have :) Is there a workaround? Is it possible to reliably have
global objects? Or is it such a bad practice that I should be deeply
ashamed :) ?

Your help would be highly appreciated.. Thanks in advance!

Yours sincerely,
Onno Broekmans

[storrboy]

On Feb 4, 6:48 am, "onn...@gmail.c om" <onn...@gmail.c omwrote:

Hi all,

Currently, I'm working on an Access XP database app that uses two
global objects in its code. These two objects are instances of
"controller classes". For example, one of them manages the multiple
open instances of a form (some sort of 'window manager').

These global objects are created in a module "General", by defining
them with e.g.:

Dim VwMng As New KViewManager

Now there seems to be a bit of a problem with these global objects:
when I'm running the application, at random times Access crashes when
the code accesses these global objects. Apparently, the instances are
sometimes reset by Access --- even though I'm not working on the code
and haven't recompiled anything explicitly.

I also tried modifying the above code with...

Dim VwMng as KViewManager

...and then explicitly doing a "Set VwMng = New KViewManager" in the
AutoExec startup function. Same problem: completely at random, the
references seem to become invalid.

It seems that I've just taken Access too far, or made things overly
complicated or so... So now I'm working to rework the code, but this
global objects problem keeps popping up --- e.g. defining an instance
of the class Collection in a module results in the same problem:
sometimes the collection just vanishes into thin air, crashing Access.

Now I'm sure that there are people in here with a lot more experience
than I have :) Is there a workaround? Is it possible to reliably have
global objects? Or is it such a bad practice that I should be deeply
ashamed :) ?

Your help would be highly appreciated.. Thanks in advance!

Yours sincerely,

Onno Broekmans

The only times I've encountered this is when there is insufficent
error handling.
Any time you get the "Debug" / "End" option in an error message, the
code will inevitably stop running and everthing is reset.
Applying proper error handling will alert you to the error and handle
it without asking you what to do. Thereby not resetting project.

[John Mishefske]

on****@gmail.co m wrote:

Now there seems to be a bit of a problem with these global objects:
when I'm running the application, at random times Access crashes when
the code accesses these global objects. Apparently, the instances are
sometimes reset by Access --- even though I'm not working on the code
and haven't recompiled anything explicitly.

Global variables are reset if there is an unhandled error. This doesn't occur in .MDE
files but does in .MDB files.

Add error-handling to appropriate procs.

Some classes can be re-instantiated but it doesn't sound like your class is a candidate if
it tracking other resources like open forms.

Public m_instanceYourC lass As clsYourClass

Public Function returnObjectRef () As clsYourClass

If (m_instanceYour Class Is Nothing) Then
Set m_instanceYourC lass = new clsYourClass
End If

Set returnObjectRef = m_instanceYourC lass
End Function

air code. Something like that but this is just curing the symptoms and not the disease ;)
--
'---------------
'John Mishefske
'---------------

[onnodb]

Hi John and storrboy,

Thanks for your replies! I'm afraid, though, that the whole project
has already been filled with error handling :) I'm pretty sure there
are no unhandled errors occurring.

I will try using John's code, but I think I already tried it once, to
no avail.

Yours sincerely,
Onno Broekmans

[onnodb]

Hm.. I also tried storing the 'global objects' on a form, but the same
problem keeps popping up: Access crashing at random when a global
object is accessed.

Is there anyone here who has used one or more global objects in a
module (like a Collection, or a home-grown object) with success? If
so, it would mean there may be some other problem in my code?

Thanks again,

Yours sincerely,
Onno Broekmans

[Tim Marshall]

on****@gmail.co m wrote:

Hm.. I also tried storing the 'global objects' on a form, but the same
problem keeps popping up: Access crashing at random when a global
object is accessed.

How did you do it?

When I follow this approach, I have a form, frmV (V for variables) with
numerous text boxes and possibly other controls on it. When I assign a
value to such a conytrol it's:

Forms.frmV.txtW indowsUserName = <whatever>

To access the variable in another form or module, I just refer back to
Forms.frmV.txtW indowsUserName
--
Tim http://www.ucs.mun.ca/~tmarshal/
^o<
/#) "Burp-beep, burp-beep, burp-beep?" - Quaker Jake
/^^ "Be Careful, Big Bird!" - Ditto "TIM-MAY!!" - Me

[storrboy]

In the Tools>Options menu, try changing the 'Break On' option to
Unhandled Errors.
See if you notice a difference in when and how many errors occur.

Try finding a method that repeates the error consistantly. Step
through the code and carefully check all your variable values and see
if you can identify what is actually causing it. This should at least
narrow down what to investigate next.

[j.huibregtse]

Hi Tim,

Hm.. I also tried storing the 'global objects' on a form, but the same
problem keeps popping up: Access crashing at random when a global
object is accessed.

How did you do it?

I declared a public variable:

Public ViewManager As CViewManager

in a form frmSys, which was opened during startup and then hidden
(Visible=False) . The variable was initialized in frmSys's Open event.
I also tried John's approach. It still seems Access 'randomly' resets
the project or so...

Yours sincerely,
Onno Broekmans

[j.huibregtse]

Hi storrboy,

In the Tools>Options menu, try changing the 'Break On' option to
Unhandled Errors.
See if you notice a difference in when and how many errors occur.

Try finding a method that repeates the error consistantly. Step
through the code and carefully check all your variable values and see
if you can identify what is actually causing it. This should at least
narrow down what to investigate next.

Thanks for the suggestion; I already have these settings set, though.
Perhaps I should indeed try stepping through the code some more. I
noticed some time ago, though, that when explicitly *stepping* through
the code in de debugger magically lets the errors disappear :)

I gave it some more thought, and it seems that most often pressing a
toolbar button causes the crash. Perhaps there could be some
(additional) problem regarding customized toolbars and toolbar buttons
bound to functions in a module?

Yours sincerely,
Onno Broekmans

[storrboy]

On Feb 5, 2:00 pm, j.huibreg...@um ail.leidenuniv. nl wrote:

Hi storrboy,

......

>
I gave it some more thought, and it seems that most often pressing a
toolbar button causes the crash. Perhaps there could be some
(additional) problem regarding customized toolbars and toolbar buttons
bound to functions in a module?

Yours sincerely,

Onno Broekmans

I once also had problems with custom toolbars, but I can't recall if
it reset the project or not.
I found that both calling subs and using functions that return values
or accept arguments in a toolbar's action did cause problems.
I have since stuck with only calling functions specific to the button.

example...

Button action: =DoThis()

Function DoThis()
'Run the actual required proceedure using need arguments and return
values
End Function