Visual Basic/VB, Global Variables over three projects

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Visual Basic/VB >> Global Variables over three projects

by Ken Halter » Wed, 08 Oct 2003 10:21:32 GMT

One problem with GlobalMultiUse is that instances are created automatically. Which means
that an entirely new instance may created when you're not expecting it. I never use
GlobalMultiUse because I want to control when and where instances are created. If you
switch to MultiUse, you'll probably find your bug.

--
Ken Halter - MS-MVP-VB - http://www.vbsight.com
Please keep it in the groups..


"Tim" < XXXX@XXXXX.COM > wrote in message
news: XXXX@XXXXX.COM ...
> Hello All,
>
> I am developing an App using VB6. I have:
>
> 1 exe file
> 1 Active X OCX
> 1 ActiveX dll
>
> Actually it is bigger than this, but for explinations sake...
>
> The Active X dll is GlobalMultiUse (GMU) and I want it to hold global
> variables that can be set and read from the other two files.
>
> I have used no code to create instances of the GMU object. I have just
> ticked it as a reference in Project References.
>
> This all work fine on my development machine (Win 2000), but when I build
> the project group and install the app onto another machine (XP Prof) Some
> (and only some) of the variables get lost between the two other files.
>
> Any ideas would be appreciated.
>
> TIA
>
> Tim
>
>



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Visual Basic/VB >> Global Variables over three projects

by Ken Halter » Wed, 08 Oct 2003 12:23:15 GMT


Here's one way... basically, you create a property that accepts the object as an argument.
'==================Form Code
Option Explicit

Private mobjClass1Instance As Class1
Private mobjClass2Instance As Class2

Private Sub Command1_Click()
Call mobjClass2Instance.ShowClass1Value
End Sub

Private Sub Form_Load()
Set mobjClass1Instance = New Class1
Set mobjClass2Instance = New Class2

'Set a value
mobjClass1Instance.TestProp = "This is a test"

'Pass the instance of Class1 to Class2
Set mobjClass2Instance.Class1Obj = mobjClass1Instance
End Sub

Private Sub Form_Unload(Cancel As Integer)
'Make sure to clear the extra reference
Set mobjClass2Instance.Class1Obj = Nothing
End Sub
'==================Class1 Code (this represents the "global" data)
Option Explicit

Public TestProp As String
'==================Class2 Code
Option Explicit

Private mobjClass1Instance As Class1

Public Property Set Class1Obj(ByRef Setting As Class1)
Set mobjClass1Instance = Setting
End Property

Public Sub ShowClass1Value()
MsgBox "mobjClass1Instance.TestProp" _
= " & mobjClass1Instance.TestProp"
End Sub
'==================



--
Ken Halter - MS-MVP-VB - http://www.vbsight.com
Please keep it in the groups..












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Visual Basic/VB >> Global Variables over three projects

by Tim » Wed, 08 Oct 2003 20:22:22 GMT

Hello All,

I am developing an App using VB6. I have:

1 exe file
1 Active X OCX
1 ActiveX dll

Actually it is bigger than this, but for explinations sake...

The Active X dll is GlobalMultiUse (GMU) and I want it to hold global
variables that can be set and read from the other two files.

I have used no code to create instances of the GMU object. I have just
ticked it as a reference in Project References.

This all work fine on my development machine (Win 2000), but when I build
the project group and install the app onto another machine (XP Prof) Some
(and only some) of the variables get lost between the two other files.

Any ideas would be appreciated.

TIA

Tim



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Global Variables over three projects

by Tim » Wed, 08 Oct 2003 23:54:42 GMT

Thanks for this Ken.

If I use MultiUse, how can I make the same instance be recognised by my
other two files at the same time.

Any help or pointers would be greatly appreciated.

Thanks

Tim



automatically. Which means
never use
created. If you


build
Some



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Global Variables over three projects

by Frampton Firesword » Thu, 09 Oct 2003 02:17:19 GMT


automatically.

They're not! I agree, they're *supposed* to, but I've experienced projects
with GlobalMultiUse things in and they are 'nothing' in the form_load event.
I think it just shows that the rigmarole and the hoops VB has to go through
to implement different types of interfaces weighs it down sometimes - and
you just have to steer clear of those and know what it's best at.
My advice is to keep it as stateless as possible - create the object when
you need it, and destroy it when you don't. If it's constant data that needs
to be in the program all the time, then have it in a .bas.


Which means
never use
created. If you


build
Some



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Global Variables over three projects

by Ken Halter » Thu, 09 Oct 2003 02:30:06 GMT

an't share "Globals" in a .bas file between multiple projects. There must've been
something else going on with your code. The reason I don't like GlobalMultiUse is that it
takes the creation/destruction stuff away from you. We had a project here that ended up
with 20 instances of a GlobalMultiUse object when they only expected one. I know it was
"programmer error" that caused the problem but still... I removed all GlobalMultiUse
classes (changed them to MultiUse) to force everyone to explicitly create instances.

The thing that attracts people to GlobalMultiUse is that they don't need to declare and
use an object variable to access the properties and methods. They basically become "part
of the language" and instantiate objects when needed. Puke on that. Declare an object
variable, instantiate the object, call it's methods, set it's properties and get rid of it
when you're done.

GlobalMultiUse is not such a good name for the behaviour anyway. There's really nothing
"Global" about it.

--
Ken Halter - MS-MVP-VB - http://www.vbsight.com
Please keep it in the groups..


"Frampton Firesword" < XXXX@XXXXX.COM > wrote in message
news: XXXX@XXXXX.COM ...



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Global Variables over three projects

by Tim » Thu, 09 Oct 2003 03:48:49 GMT

hanks for your reponses.

What is the eaisest way of declaring global variables over seperate
projects. ie. So the variables can be used from any project.

Cheers

"Ken Halter" < XXXX@XXXXX.COM > wrote in message
news:% XXXX@XXXXX.COM ...
must've been
GlobalMultiUse is that it
that ended up
I know it was
GlobalMultiUse
instances.
to declare and
basically become "part
Declare an object
and get rid of it
really nothing
projects
event.
through
and
when
needs
it. I
global
just
files.



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Global Variables over three projects

by Ken Halter » Thu, 09 Oct 2003 04:27:50 GMT

They'll need to be in a class somewhere (something like the sample I posted 10/7/2003 9:23
PM)... Note that the post date is wrong... I was messing around with my PC clock to see
what happens to some code when it hits midnight and I forgot to set it back before
posting.... here... I'll repost in case you can't find the original.

Here's one way... basically, you create a property that accepts the object as an argument.
'==================Form Code
Option Explicit

Private mobjClass1Instance As Class1
Private mobjClass2Instance As Class2

Private Sub Command1_Click()
Call mobjClass2Instance.ShowClass1Value
End Sub

Private Sub Form_Load()
Set mobjClass1Instance = New Class1
Set mobjClass2Instance = New Class2

'Set a value
mobjClass1Instance.TestProp = "This is a test"

'Pass the instance of Class1 to Class2
Set mobjClass2Instance.Class1Obj = mobjClass1Instance
End Sub

Private Sub Form_Unload(Cancel As Integer)
'Make sure to clear the extra reference
Set mobjClass2Instance.Class1Obj = Nothing
End Sub
'==================Class1 Code (this represents the "global" data)
Option Explicit

Public TestProp As String
'==================Class2 Code
Option Explicit

Private mobjClass1Instance As Class1

Public Property Set Class1Obj(ByRef Setting As Class1)
Set mobjClass1Instance = Setting
End Property

Public Sub ShowClass1Value()
MsgBox "mobjClass1Instance.TestProp" _
= " & mobjClass1Instance.TestProp"
End Sub
'==================


--
Ken Halter - MS-MVP-VB - http://www.vbsight.com
Please keep it in the groups..







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Global Variables over three projects

by dnagel » Thu, 09 Oct 2003 04:32:04 GMT

think Ken already mentioned it...

Use a Class, initialize it in Sub Main, and then pass it around to
forms or other objects that need it by hanging properties off of
those objects to receive the reference to that class object...

Any other method, albeit there might be slightly less actual typing
involved, is not going to be as robust or consistently available.

You also gain the ability to use property Let/Set/Get routines,
providing read only values as well as read/write and you can
add logic to validate those values in the property procedures.

It really is the only method you should consider. My recommendation
comes from experience through trial and error as well as reading
the brain dumps from guys like Ken... He's rarely incorrect.

D.


Tim wrote:



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Global Variables over three projects

by Tim » Thu, 09 Oct 2003 20:21:51 GMT

hanks for all your advice. I will use this method, which I now fully
understand, but didn't at first.

"dnagel" < XXXX@XXXXX.COM > wrote in message
news:% XXXX@XXXXX.COM ...
here
one.
create



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Global Variables over three projects

by Frampton Firesword » Sat, 11 Oct 2003 02:16:03 GMT

think I discovered that the problem was that although they didn't have to
create instances created of them, they did at least have to be dimmed. Which
is what I wasn't doing, I was expecting them to be like the 'Printer'
object.

But yes I agree, they are rubbish.


"Ken Halter" < XXXX@XXXXX.COM > wrote in message
news:% XXXX@XXXXX.COM ...
must've been
GlobalMultiUse is that it
that ended up
I know it was
GlobalMultiUse
instances.
to declare and
basically become "part
Declare an object
and get rid of it
really nothing
projects
event.
through
and
when
needs
it. I
global
just
files.



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