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Re: Name of subpackage dependent on main package

by davido (Cardinal)
on Dec 29, 2019 at 23:34 UTC ( #11110740=note: print w/replies, xml ) Need Help??


in reply to Name of subpackage dependent on main package

It obviously doesn't work quite how you're thinking. One of the problems is that package does not accept the namespace as a dynamic argument. The namespace must be a hard-coded string of characters. However, all is not lost. You can have everything you want, just not the way you're doing it:

package My; use strict; use warnings; my $pkg_sub = __PACKAGE__ . '::A'; # some methods for package My... { no strict 'refs'; *{$pkg_sub . '::new'} = sub { my $class = shift; return bless {ref($_[0]) ? %{$_[0]} : @_}, $class; }; *{$pkg_sub . '::greet' } = sub { print 'Hello ' . shift()->{'name' +} . ".\n"; }; } 1; package main; my $mya = My::A->new({name => 'Dave'}); $mya->greet();

You can bless a reference into any string you want. And in this case, you can assign a subroutine reference to any typeglob you want. In the example above I'm creating My::A::new, and My::A::greet. Yes, it's a little more work, but where there's work, there's a need for automation:

my %subs = ( new => sub { # constructor goes here... }, greet => sub { # Greeter goes here... }, ); while (my ($name, $code) = each %subs) { no strict 'refs'; *{$pkg_sub . '::' . $name} = $code; }

This hash based method has the advantage of releasing strict 'refs' in a much smaller scope. To be clear, you don't need a package My::A; statement to be able to create subroutines and methods in the My::A namespace; you just have to do without the conveniences package provides, crafting the subroutine namespaces manually.

And, in fact, this method is how Class:Builder works (snippet from Class::Builder):

{ # ... no strict 'refs'; # ... while (my ($name, $code) = each %methods){ *{"$class"."::"."$name"} = $code; } }

Dave

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