[AccessD] Global Variable

Scott Marcus marcus at tsstech.com
Wed May 18 06:20:29 CDT 2005


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

And like wise, use of Integer is not bad practice, only misuse...

Scott Marcus

-----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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