I'm working on a large project with heavy refactoring. Sometimes I am finding myself in the awkward position of refactoring classes in such a way that when I pass objects in argument lists, I am not interested in the class type, but in the class capabilities (similar to Ruby's "duck typing"). In short, I want this:

sub foo {
    my ($self, $object_or_class) = @_;
    die $message unless does($object_or_class, @methods);
    ...
}

[download]

This is becoming more of a problem as I find a large class which needs to be factored into two or more classes. The does() function is trivial to write (as long as one appreciates the caveats involved), but I was looking to see if there is something on the CPAN which already handles this. I see nothing, but if someone else does, I'd like to hear about it.

First pass of the does() function:

use Scalar::Util qw/blessed/;

sub does {
    my ($proto, @methods) = @_;
    return if ref $proto && ! blessed $proto;     
    my @coderefs;
    foreach my $method (@methods) {
        push @coderefs, $proto->can($method) || ();
    }
    return wantarray ? @coderefs : \@coderefs;
}

[download]

Cheers,
Ovid

New address of my CGI Course.

In reply to Class capabilities by Ovid

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