Parent property leads the circular reference

[Rattagarn V.]

Hi all,

I create the active X control which contains a lot of classes. Some
classes which are contained in this control have the parent property. This
property is for setting the reference to the parent object of that class.
Class MyClass:
Private Sub Class_Terminate
Set mParent = Nothing
End Sub

Friend Property Set Parent(vData as MyControl)
If mParent Is Nothing Then
Set mParent = vData
End If
End Property

Usercontrol:
Private Sub Usercontrol_Initialize()
Set mMyClass = New MyClass
Set mMyClass.Parent = Me
End Sub

Private Sub Usercontrol_Terminate()
Set mMyClass = Nothing
End Sub
The problem is that the "Terminate" event of usercontrol never been executed
after closing the Form which cantains this control.
How can I clean up the object reference?

Thank you very much
Rattagarn V.

[Gagan Behl]

Hi Rattagarn,

I think you could use the forms' queryunload event to unload the object.


Gagan

"Rattagarn V." <rattagarn@hotmail> wrote:
>
>Hi all,
>
> I create the active X control which contains a lot of classes. Some
>classes which are contained in this control have the parent property. This
>property is for setting the reference to the parent object of that class.
>Class MyClass:
> Private Sub Class_Terminate
> Set mParent = Nothing
> End Sub
>
> Friend Property Set Parent(vData as MyControl)
> If mParent Is Nothing Then
> Set mParent = vData
> End If
> End Property
>
>Usercontrol:
> Private Sub Usercontrol_Initialize()
> Set mMyClass = New MyClass
> Set mMyClass.Parent = Me
> End Sub
>
> Private Sub Usercontrol_Terminate()
> Set mMyClass = Nothing
> End Sub
>The problem is that the "Terminate" event of usercontrol never been executed
>after closing the Form which cantains this control.
>How can I clean up the object reference?
>
>Thank you very much
>Rattagarn V.

[Rattagarn V.]

Thank you for your response,

I can't use the forms' queryunload event because my usercontrol will
be placed on the another usercontrol.
I develop the web application which contains my control. I used a usercontrol
as the web page area and also have the array of usercontrol as frames for
holding each activeX control which I created. So user can switch to or add
more frames. The problem is that after any frame the terminated event of
each activeX control in that frame has never raised the terminated event.
I read the MSDN on-line and it advises to use TearDown method. It means
that I have to implement a method that is called for setting nothing to each
instances in my activeX control. Yes! it works, but why I don't need to
call any function of a button control likes this when the form or usercontrol
is terminated. It should be the same concept. Please advise me.
Rattagarn V.
"Gagan Behl" <gbehl@indya.com> wrote:
>
>Hi Rattagarn,
>
>I think you could use the forms' queryunload event to unload the object.
>
>
>Gagan
>
>"Rattagarn V." <rattagarn@hotmail> wrote:
>>
>>Hi all,
>>
>> I create the active X control which contains a lot of classes. Some
>>classes which are contained in this control have the parent property.
This
>>property is for setting the reference to the parent object of that class.
>>Class MyClass:
>> Private Sub Class_Terminate
>> Set mParent = Nothing
>> End Sub
>>
>> Friend Property Set Parent(vData as MyControl)
>> If mParent Is Nothing Then
>> Set mParent = vData
>> End If
>> End Property
>>
>>Usercontrol:
>> Private Sub Usercontrol_Initialize()
>> Set mMyClass = New MyClass
>> Set mMyClass.Parent = Me
>> End Sub
>>
>> Private Sub Usercontrol_Terminate()
>> Set mMyClass = Nothing
>> End Sub
>>The problem is that the "Terminate" event of usercontrol never been executed
>>after closing the Form which cantains this control.
>>How can I clean up the object reference?
>>
>>Thank you very much
>>Rattagarn V.
>

[Gagan Behl]

Rattagarn :

I fail to understand one thing clearly. When an ActiveX control's life is
limited to that of a page, then why are you worrying about destroying the
instances in the first place ?

Gagan


"Rattagarn V." <rattagarn@hotmail.com> wrote:
>
>Thank you for your response,
>
> I can't use the forms' queryunload event because my usercontrol will
>be placed on the another usercontrol.
> I develop the web application which contains my control. I used a usercontrol
>as the web page area and also have the array of usercontrol as frames for
>holding each activeX control which I created. So user can switch to or
add
>more frames. The problem is that after any frame the terminated event of
>each activeX control in that frame has never raised the terminated event.
> I read the MSDN on-line and it advises to use TearDown method. It means
>that I have to implement a method that is called for setting nothing to
each
>instances in my activeX control. Yes! it works, but why I don't need to
>call any function of a button control likes this when the form or usercontrol
>is terminated. It should be the same concept. Please advise me.
>Rattagarn V.
>"Gagan Behl" <gbehl@indya.com> wrote:
>>
>>Hi Rattagarn,
>>
>>I think you could use the forms' queryunload event to unload the object.
>>
>>
>>Gagan
>>
>>"Rattagarn V." <rattagarn@hotmail> wrote:
>>>
>>>Hi all,
>>>
>>> I create the active X control which contains a lot of classes. Some
>>>classes which are contained in this control have the parent property.

>This
>>>property is for setting the reference to the parent object of that class.
>>>Class MyClass:
>>> Private Sub Class_Terminate
>>> Set mParent = Nothing
>>> End Sub
>>>
>>> Friend Property Set Parent(vData as MyControl)
>>> If mParent Is Nothing Then
>>> Set mParent = vData
>>> End If
>>> End Property
>>>
>>>Usercontrol:
>>> Private Sub Usercontrol_Initialize()
>>> Set mMyClass = New MyClass
>>> Set mMyClass.Parent = Me
>>> End Sub
>>>
>>> Private Sub Usercontrol_Terminate()
>>> Set mMyClass = Nothing
>>> End Sub
>>>The problem is that the "Terminate" event of usercontrol never been executed
>>>after closing the Form which cantains this control.
>>>How can I clean up the object reference?
>>>
>>>Thank you very much
>>>Rattagarn V.
>>
>

[Rattagarn V.]

Thank you for you response Gagan:
Even my web application has one page only, user can add (load/unload)
any activex control they want. The problem is that each time they add a
control, it will consume the resources and memory of the system. Unfortunately,
the resources and memory are never backed after unload these controls. So
while user uses the application, the resources is reduced continueously.
The resources has never reclaimed because the terminated event of each control
has never been reached because of circular reference. How can I solve this?

Rattagarn V.

"Gagan Behl" <gbehl@indya.com> wrote:
>
>Rattagarn :
>
>I fail to understand one thing clearly. When an ActiveX control's life is
>limited to that of a page, then why are you worrying about destroying the
>instances in the first place ?
>
>Gagan
>
>
>"Rattagarn V." <rattagarn@hotmail.com> wrote:
>>
>>Thank you for your response,
>>
>> I can't use the forms' queryunload event because my usercontrol will
>>be placed on the another usercontrol.
>> I develop the web application which contains my control. I used a usercontrol
>>as the web page area and also have the array of usercontrol as frames for
>>holding each activeX control which I created. So user can switch to or
>add
>>more frames. The problem is that after any frame the terminated event
of
>>each activeX control in that frame has never raised the terminated event.
>> I read the MSDN on-line and it advises to use TearDown method. It means
>>that I have to implement a method that is called for setting nothing to
>each
>>instances in my activeX control. Yes! it works, but why I don't need to
>>call any function of a button control likes this when the form or usercontrol
>>is terminated. It should be the same concept. Please advise me.
>>Rattagarn V.
>>"Gagan Behl" <gbehl@indya.com> wrote:
>>>
>>>Hi Rattagarn,
>>>
>>>I think you could use the forms' queryunload event to unload the object.
>>>
>>>
>>>Gagan
>>>
>>>"Rattagarn V." <rattagarn@hotmail> wrote:
>>>>
>>>>Hi all,
>>>>
>>>> I create the active X control which contains a lot of classes.
Some
>>>>classes which are contained in this control have the parent property.
>
>>This
>>>>property is for setting the reference to the parent object of that class.
>>>>Class MyClass:
>>>> Private Sub Class_Terminate
>>>> Set mParent = Nothing
>>>> End Sub
>>>>
>>>> Friend Property Set Parent(vData as MyControl)
>>>> If mParent Is Nothing Then
>>>> Set mParent = vData
>>>> End If
>>>> End Property
>>>>
>>>>Usercontrol:
>>>> Private Sub Usercontrol_Initialize()
>>>> Set mMyClass = New MyClass
>>>> Set mMyClass.Parent = Me
>>>> End Sub
>>>>
>>>> Private Sub Usercontrol_Terminate()
>>>> Set mMyClass = Nothing
>>>> End Sub
>>>>The problem is that the "Terminate" event of usercontrol never been executed
>>>>after closing the Form which cantains this control.
>>>>How can I clean up the object reference?
>>>>
>>>>Thank you very much
>>>>Rattagarn V.
>>>
>>
>

[Michael Culley]

Rattagarn,

>because of circular reference

This is your answer here. You have to avoid circular references. To do this
you have to keep a reference to your usercontrol without your usercontrol
knowing you have it. In the class, change the parent Set/Get to this

private mlngParent as long

Public property Set Parent(ByVal RHS as MyControl)
mlnParent=objptr(rhs)
end property

Public property Get Parent() as MyControl
Set MyControl=ResolveObjPtr ( mlngParent)
End Property

Private Function ResolveObjPtr(ByVal Pointer as long) as object
Dim x as object
copymemory x,pointer,4&
set resolveobjptr=x
copymemory x,0&,4&
end function

Then in your usercontrol Terminate event

Set MyClass.Parent=Nothing

There is plenty of info on this topic all over the web. Just search for stolen
reference, cicular reference or weak reference.


Michael Culley


"Rattagarn V." <rattagarn@hotmail.com> wrote:
>
>Thank you for you response Gagan:
> Even my web application has one page only, user can add (load/unload)
>any activex control they want. The problem is that each time they add a
>control, it will consume the resources and memory of the system. Unfortunately,
>the resources and memory are never backed after unload these controls.
So
>while user uses the application, the resources is reduced continueously.
> The resources has never reclaimed because the terminated event of each
control
>has never been reached because of circular reference. How can I solve this?
>
>Rattagarn V.
>
>"Gagan Behl" <gbehl@indya.com> wrote:
>>
>>Rattagarn :
>>
>>I fail to understand one thing clearly. When an ActiveX control's life
is
>>limited to that of a page, then why are you worrying about destroying the
>>instances in the first place ?
>>
>>Gagan
>>
>>
>>"Rattagarn V." <rattagarn@hotmail.com> wrote:
>>>
>>>Thank you for your response,
>>>
>>> I can't use the forms' queryunload event because my usercontrol will
>>>be placed on the another usercontrol.
>>> I develop the web application which contains my control. I used a
usercontrol
>>>as the web page area and also have the array of usercontrol as frames
for
>>>holding each activeX control which I created. So user can switch to or
>>add
>>>more frames. The problem is that after any frame the terminated event
>of
>>>each activeX control in that frame has never raised the terminated event.
>>> I read the MSDN on-line and it advises to use TearDown method. It
means
>>>that I have to implement a method that is called for setting nothing to
>>each
>>>instances in my activeX control. Yes! it works, but why I don't need
to
>>>call any function of a button control likes this when the form or usercontrol
>>>is terminated. It should be the same concept. Please advise me.
>>>Rattagarn V.
>>>"Gagan Behl" <gbehl@indya.com> wrote:
>>>>
>>>>Hi Rattagarn,
>>>>
>>>>I think you could use the forms' queryunload event to unload the object.
>>>>
>>>>
>>>>Gagan
>>>>
>>>>"Rattagarn V." <rattagarn@hotmail> wrote:
>>>>>
>>>>>Hi all,
>>>>>
>>>>> I create the active X control which contains a lot of classes.

>Some
>>>>>classes which are contained in this control have the parent property.
>>
>>>This
>>>>>property is for setting the reference to the parent object of that class.
>>>>>Class MyClass:
>>>>> Private Sub Class_Terminate
>>>>> Set mParent = Nothing
>>>>> End Sub
>>>>>
>>>>> Friend Property Set Parent(vData as MyControl)
>>>>> If mParent Is Nothing Then
>>>>> Set mParent = vData
>>>>> End If
>>>>> End Property
>>>>>
>>>>>Usercontrol:
>>>>> Private Sub Usercontrol_Initialize()
>>>>> Set mMyClass = New MyClass
>>>>> Set mMyClass.Parent = Me
>>>>> End Sub
>>>>>
>>>>> Private Sub Usercontrol_Terminate()
>>>>> Set mMyClass = Nothing
>>>>> End Sub
>>>>>The problem is that the "Terminate" event of usercontrol never been
executed
>>>>>after closing the Form which cantains this control.
>>>>>How can I clean up the object reference?
>>>>>
>>>>>Thank you very much
>>>>>Rattagarn V.
>>>>
>>>
>>
>

[Bill Storage]

If you'd like more details on Michaels solution, I've got an article on my
site that might help:

http://www.bstorage.com/NerveNet/Sub...hAddressOf.asp

Bill Storage



Rattagarn V. <rattagarn@hotmail.com> wrote in message
news:39c21284$1@news.devx.com...
>
> Thank you for you response Gagan:
> Even my web application has one page only, user can add (load/unload)
> any activex control they want. The problem is that each time they add a
> control, it will consume the resources and memory of the system.
Unfortunately,
> the resources and memory are never backed after unload these controls. So
> while user uses the application, the resources is reduced continueously.
> The resources has never reclaimed because the terminated event of each
control
> has never been reached because of circular reference. How can I solve
this?
>
> Rattagarn V.
>
> "Gagan Behl" <gbehl@indya.com> wrote:
> >
> >Rattagarn :
> >
> >I fail to understand one thing clearly. When an ActiveX control's life is
> >limited to that of a page, then why are you worrying about destroying the
> >instances in the first place ?
> >
> >Gagan
> >
> >
> >"Rattagarn V." <rattagarn@hotmail.com> wrote:
> >>
> >>Thank you for your response,
> >>
> >> I can't use the forms' queryunload event because my usercontrol will
> >>be placed on the another usercontrol.
> >> I develop the web application which contains my control. I used a
usercontrol
> >>as the web page area and also have the array of usercontrol as frames
for
> >>holding each activeX control which I created. So user can switch to or
> >add
> >>more frames. The problem is that after any frame the terminated event
> of
> >>each activeX control in that frame has never raised the terminated
event.
> >> I read the MSDN on-line and it advises to use TearDown method. It
means
> >>that I have to implement a method that is called for setting nothing to
> >each
> >>instances in my activeX control. Yes! it works, but why I don't need to
> >>call any function of a button control likes this when the form or
usercontrol
> >>is terminated. It should be the same concept. Please advise me.
> >>Rattagarn V.
> >>"Gagan Behl" <gbehl@indya.com> wrote:
> >>>
> >>>Hi Rattagarn,
> >>>
> >>>I think you could use the forms' queryunload event to unload the
object.
> >>>
> >>>
> >>>Gagan
> >>>
> >>>"Rattagarn V." <rattagarn@hotmail> wrote:
> >>>>
> >>>>Hi all,
> >>>>
> >>>> I create the active X control which contains a lot of classes.
> Some
> >>>>classes which are contained in this control have the parent property.
> >
> >>This
> >>>>property is for setting the reference to the parent object of that
class.
> >>>>Class MyClass:
> >>>> Private Sub Class_Terminate
> >>>> Set mParent = Nothing
> >>>> End Sub
> >>>>
> >>>> Friend Property Set Parent(vData as MyControl)
> >>>> If mParent Is Nothing Then
> >>>> Set mParent = vData
> >>>> End If
> >>>> End Property
> >>>>
> >>>>Usercontrol:
> >>>> Private Sub Usercontrol_Initialize()
> >>>> Set mMyClass = New MyClass
> >>>> Set mMyClass.Parent = Me
> >>>> End Sub
> >>>>
> >>>> Private Sub Usercontrol_Terminate()
> >>>> Set mMyClass = Nothing
> >>>> End Sub
> >>>>The problem is that the "Terminate" event of usercontrol never been
executed
> >>>>after closing the Form which cantains this control.
> >>>>How can I clean up the object reference?
> >>>>
> >>>>Thank you very much
> >>>>Rattagarn V.
> >>>
> >>
> >
>