[AccessD] Global Variable

dmcafee at pacbell.net dmcafee at pacbell.net
Tue May 17 15:48:49 CDT 2005


Besides, everyone knows that the only time you should ever use a Global is
when its being called from a macro to populate part of a natural key on a
bound form :P

D

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com]On Behalf Of Charlotte
Foust
Sent: Tuesday, May 17, 2005 1:34 PM
To: Access Developers discussion and problem solving
Subject: RE: [AccessD] Global Variable


Give it up, John.  When Drew decides no one elses arguments make any
sense, there's no reasoning with him. ;->

Charlotte Foust


-----Original Message-----
From: John W. Colby [mailto:jwcolby at colbyconsulting.com]
Sent: Tuesday, May 17, 2005 1:06 PM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Global Variable


ROTFL.

John W. Colby
www.ColbyConsulting.com

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of
DWUTKA at marlow.com
Sent: Tuesday, May 17, 2005 3:58 PM
To: accessd at databaseadvisors.com
Subject: RE: [AccessD] Global Variable


You have said that using Globals is bad practice, which it is not.  That
is my argument.  The misuse is.  'Getting carried away with'...well,
that's an iffy statement, because you have to judge what is 'getting
carried away with' and what is not.

Drew

-----Original Message-----
From: John W. Colby [mailto:jwcolby at colbyconsulting.com]
Sent: Tuesday, May 17, 2005 2:02 PM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Global Variable


Would "getting carried away with globals" be considered misuse of
globals? If you look back to the first post you see that is what I
warned against. Notice I did NOT tell him that in his particular case he
should not use a global.

YOU have built an argument for your own amusement, but in the end it has
enabled us to discuss the issue which is a good thing.

John W. Colby
www.ColbyConsulting.com

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of
DWUTKA at marlow.com
Sent: Tuesday, May 17, 2005 2:40 PM
To: accessd at databaseadvisors.com
Subject: RE: [AccessD] Global Variable


Ah.  There's the issue.  'If a global doesn't need to be SET by project
wide code'.  Okay.  Now, that I will back down on.  I personally don't
have an issue with setting it one place, and using it other places.  No
problem there.  But what if you are constantly using (reading and
writing) it from many places in your project.  Does a Global Variable
fit the model?  Of course!  Honestly, I use classes too, and will make
read only properties 'read only'.

Drew

P.S.-- Still doesn't make Globals bad practice, only misuse of
globals...which is still my position.



-----Original Message-----
From: John W. Colby [mailto:jwcolby at colbyconsulting.com]
Sent: Tuesday, May 17, 2005 11:52 AM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Global Variable


I understand completely Drew.  In order to not use globals you have to
THINK and you are too busy typing to do that.

Correct me if I am wrong, but nowhere did I advocate any code like you
mentioned.  Can you show me where in my email I advocated that?  What I
said was that if a global doesn't need to be SET by project wide code
then it doesn't need to be global.

I have seen in your previous posts where you mention saving keystrokes.
Understand that I am NOT a data entry person.  My job is to design well
engineered systems.  If that means more keystrokes, so be it.

John W. Colby
www.ColbyConsulting.com

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of
DWUTKA at marlow.com
Sent: Tuesday, May 17, 2005 11:32 AM
To: accessd at databaseadvisors.com
Subject: RE: [AccessD] Global Variable


Tighter?  If I looked at code like this:

Dim MyModuleLevelString as String
Private Function SetModuleLevelString(strValueToSet As String)
MyModuleLevelString=strValueToSet End Function

I would think the developer was getting paid by the key stroke.....not
that it was 'tight code'.

Drew

-----Original Message-----
From: John W. Colby [mailto:jwcolby at colbyconsulting.com]
Sent: Tuesday, May 17, 2005 6:59 AM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Global Variable


Gustav,

This is nothing new, and not something I take credit for figuring out.
It is not uncommon when you work with classes to have methods set the
values of and return the values from class properties.  In fact with
classes you have syntax constructs specifically for this - property
get/set/let.  You can, if you wish, dim a variable public in the class
header and then it is just read / write to anyone with a pointer to the
class.  Or you use a property get and or set/let in whatever combination
you need.  A read-only value has only a property get.  A Write-only has
only a property set (not very common) and a read / write has a property
get and property let/set.

The objective is simply to control how the variable is read/written.
Since the variable is dimensioned private to the module (or class), only
a function in the module or class can set the value, and only a function
in the module or class can return the value.  To make a property "read
only", create only a function that returns the value, but do not build a
function that sets the value.  Then only the class or module itself can
set the variable.

For example as the module initializes, perhaps some value is pulled from
a table and written into the variable.  Then a function returns the
value to any process that needs the value.  Or perhaps the value is
calculated by some math transformation using other values in other
variables.  The other variables are set by processes, but in order to
read out the value, a function either returns the variable directly or
returns the value of the mathematical transformation using the values in
the other variables.

This is not new stuff, I did not invent it, but it is commonly used to
"replace" global variables such that the CONCEPT of a global variable
exists (can be seen from anywhere) but still protects the variable from
being written when it shouldn't be or by processes that should not be
able to write to the variable.

And yes, it is more work.  It is just one of those things that you do or
your don't.  If you accept the practice, then you start thinking about
protecting variables, using variable scope, and using functions to set /
return values where appropriate.  It becomes habit and your code becomes
a little bit tighter.

John W. Colby
www.ColbyConsulting.com

Contribute your unused CPU cycles to a good cause:
http://folding.stanford.edu/

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Gustav Brock
Sent: Tuesday, May 17, 2005 6:30 AM
To: accessd at databaseadvisors.com
Subject: RE: [AccessD] Global Variable


Hi John

Well, here we have full control on where functions put their nasty
fingers.

I haven't managed yet to build self generating code; to some this would
indicate a brave new world, to some it would be a nightmare - functions
creeping around and attacking our globals and eating our children...
gosh. But worse, they would soon learn how to take advantage of your
functions to change those "private variables"! Be prepared.

/gustav

>>> jwcolby at colbyconsulting.com 05/16 10:58 pm >>>

..  Making this a global allows functions
that have no business setting these variables to change them.  By having
a private variable returned by a public function, any function that
needs the information can get it but cannot modify it.

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