NAME

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

VERSION

       version 0.32

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 or 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 recommended 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 called 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.

SUPPORT

       Bugs may be submitted through the RT bug tracker
       <https://rt.cpan.org/Public/Dist/Display.html?Name=Data-Visitor> (or
       bug-Data-Visitor@rt.cpan.org <mailto:bug-Data-Visitor@rt.cpan.org>).

AUTHORS

       •   Yuval Kogman <nothingmuch@woobling.org>

       •   Marcel Grünauer <marcel@cpan.org>

COPYRIGHT AND LICENCE

       This software is copyright (c) 2023 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.