[Chicago-talk] Dynamic method call

Steven Lembark lembark at jeeves.wrkhors.com
Thu Nov 6 19:34:44 CST 2003

> my $sub = $object->can( $method );
> &$sub(@arg);
  NO!!! The use of & to make calls is a holdover from Perl4...

Avoid using & for any sort of sub call unless you really
do understand what you are doing with it (at which point
you usually won't do it).

	my $method = $item->can( $method_name );

	$method->( $item );

is what you are looking for. You want to dereference the
method, NOT call it bypassing prototype def's with the
same @_ as the current call by default.

Note: you can use:

	sub dispatch
		my $item = shift;

		my $name = shift;

		if( my $sub = $item->can( $name ) )
			$sub->( $item, @_ )
			my $type = ref $item || $item;

			die "Bogus dispatch: $type cannot $name";

Is a fairly general dispatcher:

	$foo->dispatch( $methodnames{$inputvalue}, @otherargs );

will get redispatched as necessary. This is nice for
data-driven programming where $inputvalue can be stored
in a config file or input stream and handled by several
objects which can cooperate in dealing with the issue.

Steven Lembark                               2930 W. Palmer
Workhorse Computing                       Chicago, IL 60647
                                            +1 888 359 3508

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