From: "Tiemo Hollmann TB" <[EMAIL PROTECTED]>
on various sites - and again in this best practice thread - it is
recommended not to use globals, or at least so less as possible, because
they can be changed from everywhere and that's hard to debug and no nice
style. I really don't see any difference between using globals or
properties
yet. Properties can be changed also "from everywhere" and even if you
write a central handler to change your properties, this handler can be
called from
everywhere. What is the best practice for statuses, flags and all these
global informations, you need at different times and in different
handlers?
And if there is a "clean pratice", what is the difference to using
globals?
Globals are a kind of variable. As you note it's considered best practice
in most programming languages to avoid using them unless absolutely
necessary. However they can come in handy for some things. Generally a
local variable is safer because it's scope is within the procedure (in Rev
the on statement) or function. Limiting scope to local limits the chance of
accidentlal results (or undesirable or unpredicted results). I'd not
recommend somebody new to programming to use globals at all until they've
had some experience debugging and understanding scope.
Properties need to be thought of as pieces of an object. For example. A
Cat. A Cat has legs. Legs are properties of cats. Cats pretty much have
four legs (barring a major accident for the moggy) so it's safe to assume
there will always be four legs (properties) of a Cat. This is just like a
button object. The button always, for example, a label property unless we
create a button that does not (which is no mean feat in a technically non
object orientated language like Rev which doesn't allow decendent classes
like some other languages - in the strictest sense of the word). So the
Label is always there and we know we can stick in some text into myButton or
into theOtherButton and we are safe. Quite distinct to a variable which is
declared in our code (locally or globally). Variables don't have
properties.
Flags... Not sure what you mean here...?
Best practice is to comment your code. Just because you know what your
variable does today doesn't mean you will tomorrow or next year (or ten
years from now). So comment, comment and comment. This is critical with
globals. Name your local variables in a manner that *you* can easily see at
a glance that they are local variables and if you absolutely have to use a
global make sure you lable it clearly to and document it so that you don't
use the name somewhere else and potentially cause problems for yourself.
I'd recommend taking a look at how these things are done in some of the
example stack available on RevOnline. Many of these are exemplar and worthy
of perusal.
Scott Kane
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