debian man page for data::visitor::callback

Data::Visitor::Callback(3pm)				User Contributed Perl Documentation			      Data::Visitor::Callback(3pm)

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

VERSION
       version 0.28

SYNOPSIS
	       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 );

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

METHODS
       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.

CALLBACKS
       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.

AUTHORS
       o   Yuval Kogman <nothingmuch@woobling.org>

       o   Marcel Gruenauer <marcel@cpan.org>

COPYRIGHT AND LICENSE
       This software is copyright (c) 2012 by Yuval Kogman.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

perl v5.14.2							    2012-02-12					      Data::Visitor::Callback(3pm)