dynamic symbol Exporter

bsdz has asked for the wisdom of the Perl Monks concerning the following question:

Is it possible to export symbols dynamically in a module? For example: -

package A;

use strict;

require Exporter;
our @ISA    = qw(Exporter);
our @EXPORT = qw( build_funcs );

sub build_funcs {

    foreach ('A', 'B', 'C') {
        eval  "
        print \"building $_ func\\n\";
        sub ${_}_func {
            print \"$_ func called\\n\";
        }
        ";
        push @EXPORT, "${_}func";
    }
}
1;
[download]

Using a test function like: -

use strict;
use lib '.';
use A;

&build_funcs;

&A_func;
[download]

Any experience with this one?

Comment on dynamic symbol Exporter Select or Download Code

Replies are listed 'Best First'.
Re: dynamic symbol Exporter by broquaint (Abbot) on Nov 15, 2003 at 20:28 UTC
It is indeed possible. Perhaps you want something like this `sub build_functions { my(@funcs, $pkg) = (@_, scalar caller); for my $f (@funcs) { *{"$pkg\::$f"} = sub { print "I am &$f\n" }; } } build_functions qw/ foo bar baz /; foo(), bar(), baz(); __output__ I am &foo I am &bar I am &baz` [download] So that just creates the given arguments as dummy functions in the caller's symbol table. See. `caller` and Of Symbol Tables and Globs for more info. HTH `_________ broquaint`	[reply] [d/l]
Re: dynamic symbol Exporter by simonm (Vicar) on Nov 15, 2003 at 20:28 UTC
Building subs and pushing them onto `@EXPORT` or `@EXPORT_OK` isn't uncommon; I use this same technique in Text::MicroMason. However, looking at your code, I think you'll need to move the `&build_funcs;` call to the end of package A, so that it's executed before the `use A` completes.	[reply] [d/l] [select]
Re: dynamic symbol Exporter by !1 (Hermit) on Nov 15, 2003 at 20:30 UTC
Your code is just defining the subroutines within the A namespace. You could use caller to return the namespace in which you want the subroutine exported. `sub build_funcs { my $package = caller; foreach ('A', 'B', 'C') { eval " print \"building $_ func\\n\"; sub $package\::${_}_func { print \"$_ func called\\n\"; } "; push @EXPORT, "${_}func"; } }` [download] Of course, you could also use AutoLoader in combination with @ISA in your test script to have an AUTOLOAD that creates the subroutine for you. Also, on a side note, don't get in the habit of calling subroutines as &sub unless you know why you're doing it. Instead use sub(). Read perldoc perlsub for more information about it. I hope this helps you with your problem.	[reply] [d/l]
Re: dynamic symbol Exporter by bsb (Priest) on Dec 22, 2003 at 09:32 UTC
Depending on the real context, you man also want to write you own import routine. perlmod for details.	[reply]