Re: How to export a package sitting lower in a module?

[kennethk]

use is an execution of require and import wrapped in a BEGIN block. Because you have package pack_B in the same file as package pack_A, you are failing the require. So the solution is to add the export text (as Corion says) and then invoke import directly, i.e. pack_B->import.

The better way (IMHO) to do this is to actually respect the package system intent and put pack_B in a different file, and don't surprise your maintainers.

[HelenCr]

Corion and kennethk:

It works best if you put separate packages into separate files.

Sometimes (especially if you have an object-oriented project, with many little packages), it's not convenient to have each package in a speparate file.

So the solution is to add the export text (as Corion says) and then invoke import directly, i.e. pack_B->import.

Please note that this still doesn't work: the .pm module fails, complaining that the second @ISA is a bareword.

Main script:

use pack_A;
pack_B->import;
third();

The packages:

# Name of this file: pack_A.pm
package pack_A;
use strict;
require Exporter;
@ISA = qw {Exporter};
@EXPORT = qw {first second};

sub first {
}
sub second {
}
1;
#end package pack_A;

package pack_B;
use strict;
require Exporter;
@ISA = qw {Exporter};
@EXPORT = qw {third fourth};
sub third {
}
sub fourth {
}
1;
#end package pack_B;
#end of file pack_A.pm

[kennethk]

Sometimes (especially if you have an object-oriented project, with many little packages), it's not convenient to have each package in a speparate file.

If you are doing OO programming in Perl, you don't need to import anything. Using packages as libraries and exporting subroutines into a user space is actually a direct contradiction with a rigid OO model.

Please note that this still doesn't work: the .pm module fails, complaining that the second @ISA is a bareword.

That's because you're violating strict. Try our:

package pack_B;
use strict;
require Exporter;
our @ISA = qw {Exporter};
our @EXPORT = qw {third fourth};
sub third {
}
sub fourth {
}
1;

[HelenCr]

Thank you, kennethk. That works (provided that you use "our @ISA" and "our @EXPORT" both in the first (pack_A) and the second (pack_B) packages).

Many thanks - Helen