Subroutines with the same name, in different packages

[mboudreau]

I can't find this situation discussed in "Programming Perl" (the camel book), "Perl Cookbook" (Christiansen & Torkington), or "Object Oriented Perl" (Conway), but I'm afraid it's a basic OO question with an obvious answer I've just missed. I throw myself on the mercy of the Monks.

I have two packages, "NLMWriter" and "ManifestWriter", that each have subroutines with common names: "new" (a constructor) and "writeInstance" (writes out an XML fragment using data from the newly constructed object).

I assume lots of packages use "new" as the name of their constructor.

When I try to use both packages in a script, I get the "subroutine redefined" error when the second package is loaded. It seems to me that this should be possible, and I should simply have to call each subroutine with the correct package name to avoid confusion, e.g.,

my $nlmwriter = new UCP::NLMWriter;
$nlmwriter->writeInstance();

What am I missing?

Package 1

package UCP::NLMWriter;

use strict;
use vars qw(@ISA @EXPORT @EXPORT_OK $VERSION $debug);

require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(&new &writeInstance);
@EXPORT_OK = ();

$VERSION = 1.0;
$debug = 0;

sub new {
   # stuff here
}

sub writeInstance {
   # stuff here
}
1;

Package 2 looks nearly the same, with different code in the "new" and "writeInstance" subroutines.

My test script:

#!/usr/bin/perl -w

use strict;

use UCP::NLMWriter;

use UCP::ManifestWriter;

[toolic]

Try not exporting those 2 subs:

@EXPORT = ();

[AnomalousMonk]

Try not exporting those 2 subs ... don't export methods.

... and if you cannot redefine what the module exports by default, suppress importation when you use the module.
    use UCP::NLMWriter ();
    use UCP::ManifestWriter ();

[mboudreau]

Thanks, all!

[Anonymous Monk]

Indeed. To the OP: exporting OO methods serves no purpose. Exporting puts the sub into the importer's package, eg main.

But when you call a method, you (usually) use the package name or an instance of that package, eg my $foo = Foo->new(); $foo->frob();. All the calling package (usually) needs to do is to use Foo; so that the class you're going to be using is loaded.

In short: don't export methods.