[AccessD] Global Vars (was Ambiguous Name)

Good advice.

The points I want to emphasize are:
* Write privately, read publicly is inherently safer scheme than globals
anybody can change
* A small number of carefully defined globals are much more managable than
the practice of indescriminately using globals by default
* Coding for the smallest scope possible, while indisputably good practice,
is also a good way to limit the harm abuse of globals can cause
-Ken

jwcolby:
> > The only advantage I see to the wrapper is that you get to set a
> breakpoint.
>
> A little more help that that.  You can add code that logs the change and
> the time of day, the workstation running the code or whatever you can think
> of that might help you troubleshoot the issue.
>
> You can add code that limits the values that can go into the variable.
>  Perhaps the global is a date and the date should never be before D day, but
> somehow it is being set to the date of black friday.  Perhaps it is a
> currency and should never be negative.  Perhaps it is a long that should
> only be between 1000 and 10000.  Perhaps it is a date that must always be
> between two other date variables.
>
> Properties exist because they allow you to do validations.  Today (when you
> define the global variable) you cannot imagine that you would ever need such
> a thing, yet in six months you see six very good reasons.
>
> Properties can be read-only (from outside of the module) or write only
> (from outside of the module).  Globals are just a variable that anyone can
> set at any time for any reason.
>
> I have lots of "globals" which can be set from inside of the module but
> only read from outside (through a property).  These are "global" in that
> anything anywhere can read them, but not write them.
>
> There are lots of programmers that have thousands of variables that are
> global, everything in sight.  There are others that have a dozen carefully
> selected.  I have a dozen, carefully selected, but I do in fact have a dozen
> or so.  I use a lot of class and module private variables in the header area
> (global to the class or module).
>
> The simple truth is that no variable should have scope beyond what is
> needed for that variable. Scope exists for a reason.  Global would not exist
> if it were not occasionally necessary.  Module and class "global" (private
> in the header of the module and class) exist because they are needed. They
> are still global but only to that module or class.  If it were good practice
> to make everything global then having private keywords would be unnecessary.
>
> John W. Colby
> www.ColbyConsulting.com
>
>