SPUG: Scope question
cmeyer at helvella.org
Wed Jun 12 01:54:59 CDT 2002
> The ::'s aren't meaningful, except to the author of the code (i.e. there's
> not any explicit inheritence between namespaces).
I meant *implicit*. There's no implicit inheritence between similarly
named namespaces. All inheritence and aliasing between namespaces is
very explicit with mechanisms like the @ISA array and the Exporter
A reference for further reading: perldoc perlsub
- which 'perldoc -f package' or 'perldoc -f my' lead you to. Scoping in
Perl is discussed throughout the document.
I am in full agreement with Jason's comment about passing parameters
around explicitly. In fact, I read a corny quote from _Code Complete_ at
last month's SPUG meeting to that effect, about parameters being a kiss
on the lips between routines (who's goal is strong cohesion via loose
coupling - or something like that ;-). That is, it gives me a headache
to search around for the meaning of a global variable, when I find it
randomly accessed from deep within some routine of some module.
However, there are perfecty valid uses for global variables. In a module
that is used for manipulating data in a relational database, how tired
do you get of passing around the database handle into each routine, or
accessing it from buried within your object. Just put it in a global,
document that to be your API, and use it when needed. Another fine use
of a global is to hold application configuration data.
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