-- Randal L. Schwartz, Perl hacker

I realise that global variables are not a very good idea. But can someone sugegst a better design ??

In the example above, I need to pass my Proxy details to each module B.pm and C.pm so that they can fetch individual docs. from the Internet. Now there are three ways of doing it, as far as I can see.

1. Pass the value individually to each module.
2. Insert the proxy value into a config file that is opened by each module.
3. Set the proxy value for A.pm and then use it for B.pm and C.pm

Now I do not like (1) so much because I need to pass the same value again and again to each module.

I do not like (2) so much because I want to keep the config as simple as possible - Nothing extra other than the config needed for basic PERL modules.

Thus I came down to (3).

Any other suggestions ??

Can you give real names to A, B, and C? What roles are they playing? Can B and C be specializations (subclasses) of A? Can B and C ask A what the current proxy setting is? If you had three people named A, B, and C, what would their job titles be, what would each of them know, and what would they have to get from each other?

A global variable is like person B riffling through the desk drawers belonging to person A just to get some info he knows. It's better to ask, not steal from behind. Because what happens if person A no longer puts it in the same drawer?

-- Randal L. Schwartz, Perl hacker

However, you did ask, so--this seems to work. I've only done B.pm, not C.pm, because they should be quite similar if I understand what you're asking.

Here's A.pm (your $i_am_the_problem is now called $problem):

    package A;
    use strict;
    use vars qw/@EXPORT @ISA $problem/;

    use Exporter;
    @ISA = qw/Exporter/;
    @EXPORT = qw/$problem/;

    1;
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    package B;
    use strict;
    use vars qw/@ISA @EXPORT/;

    use A;
    use Exporter;
    @ISA = qw/Exporter/;
    @EXPORT = qw/foo/;

    sub foo { print "problem is $problem\n" }

    1;
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    use A;
    use B;

    $problem = "bar";
    foo();
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You could, if you go with AgentM's suggestion (and you should listen to merlyn's advice), set up a method in A.pm that would look like so (assuming your object is a reference to an anonymous hash):

sub the_problem {
    my $self = shift;
    $self->{_the_problem} = shift if (@_); # sets _the_problem to the 
+value we've been passed *if* we've been passed a value
    $self->{_the_problem}; # returns the current value of _the_problem
}
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It's important to put this method in A.pm so B and C can inherit this method.

In the script which uses the modules, you would then set this property by calling the method with arguments.

use strict;
use A::B::C; #use your modules.  Pay attention to btrott's advice abov
+e on Exporter etc.
...

my $foo = new A::B::C;
$foo->the_problem("argle bargle"); # $foo->{_the_problem} now eq 'argl
+e bargle'

print $foo->the_problem();     # prints "argle bargle"
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Philosophy can be made out of anything. Or less -- Jerry A. Fodor

AgentM Systems nor Nasca Enterprises nor Bone::Easy nor Macperl is responsible for the comments made by AgentM. Remember, you can build any logical system with NOR.

$A::i_am_prob=27;

package B; # now in package B

print $A::i_am_prob; # prints 27

package C; # now in package C

print $A::i_am_prob; # prints 27
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