Data::Visitor::Callback - A Data::Visitor with callbacks.

	use Data::Visitor::Callback;

	my $v = Data::Visitor::Callback->new(
		# you can provide callbacks
		# $_ will contain the visited value

		value => sub { ... },
		array => sub { ... },




		# you can also delegate to method names
		# this specific example will force traversal on objects, by using the
		# 'visit_ref' callback which normally traverse unblessed references

		object => "visit_ref",




		# you can also use class names as callbacks
		# the callback will be invoked on all objects which inherit that class

		'Some::Class' => sub {
			my ( $v, $obj ) = @_; # $v is the visitor

			...
		},
	);

	$v->visit( $some_perl_value );

This is a Data::Visitor subclass that lets you invoke callbacks instead of needing to subclass yourself.

new %opts, %callbacks

Construct a new visitor.

The options supported are:

ignore_return_values

When this is true (off by default) the return values from the callbacks are ignored, thus disabling the fmapping behavior as documented in Data::Visitor.

This is useful when you want to modify $_ directly

tied_as_objects

Whether ot not to visit the tied in perlfunc of a tied structure instead of pretending the structure is just a normal one.

See visit_tied in Data::Visitor.

Use these keys for the corresponding callbacks.

The callback is in the form:

	sub {
		my ( $visitor, $data ) = @_;

		# or you can use $_, it's aliased

		return $data; # or modified data
	}

Within the callback $_ is aliased to the data, and this is also passed in the parameter list.

Any method can also be used as a callback:

	object => "visit_ref", # visit objects anyway

visit

Called for all values

value

Called for non objects, non container (hash, array, glob or scalar ref) values.

ref_value

Called after value, for references to regexes, globs and code.

plain_value

Called after value for non references.

object

Called for blessed objects.

Since visit_object in Data::Visitor will not recurse downwards unless you delegate to visit_ref, you can specify visit_ref as the callback for object in order to enter objects.

It is reccomended that you specify the classes (or base classes) you want though, instead of just visiting any object forcefully.

Some::Class

You can use any class name as a callback. This is colled only after the object callback.

If the object isa the class then the callback will fire.

These callbacks are called from least derived to most derived by comparing the classes' isa at construction time.

object_no_class

Called for every object that did not have a class callback.

object_final

The last callback called for objects, useful if you want to post process the output of any class callbacks.

array

Called for array references.

hash

Called for hash references.

glob

Called for glob references.

scalar

Called for scalar references.

tied

Called on the return value of tied for all tied containers. Also passes in the variable as the second argument.

seen

Called for a reference value encountered a second time.

Passes in the result mapping as the second argument.

Yuval Kogman <nothingmuch@woobling.org>

	Copyright (c) 2006 Yuval Kogman. All rights reserved
	This program is free software; you can redistribute
	it and/or modify it under the same terms as Perl itself.