Contributed by btrott
on Apr 21, 2000 at 03:37 UTC
Q&A
> object-oriented programming
Answer: How do I create static class variables (class data)? contributed by btrott Perl doesn't have a special syntax for creating such
variables. All you have to do, basically, is declare
a lexical variable at the start of the file in which
you're declaring your class, like
package Foo;
my $Bar = 0;
It's important to declare it with my rather than as
a package global, because the latter could be accessed
directly by scripts using your class--and you don't
want that (well, most likely you don't).
You shouldn't just use this variable directly in your
class, though, because your class won't be very
inheritable. Subclasses that inherit your methods will
be altering *your* class variable rather than their
own; you don't want this.
To fix this, take a reference to the data and store it
in your objects. For example, say that you have an
object that's really a hash reference--to give it
access to your class data, you could do this:
$self->{'_BAR'} = \$Bar;
in your constructor. When you want to access the class
data, then, just use it like you would a regular
reference:
print "\$Bar is currently ", ${ $self->{'_BAR'} };
And there you go! Your very own static member.
For more information and for some practical uses of
such a variable, take a look at perltoot. | Answer: How do I create static class variables (class data)? contributed by chromatic The new keyword our (introduced in Perl 5.6) provides a package scope for variables. It is demonstrated in perltootc. |
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