NAME

       Data::Clone - Polymorphic data cloning

VERSION

       This document describes Data::Clone version 0.004.

SYNOPSIS

           # as a function
           use Data::Clone;

           my $data   = YAML::Load("foo.yml"); # complex data structure
           my $cloned = clone($data);

           # makes Foo clonable
           package Foo;
           use Data::Clone;
           # ...

           # Foo is clonable
           my $o = Foo->new();
           my $c = clone($o); # $o is deeply copied

           # used for custom clone methods
           package Bar;
           use Data::Clone qw(data_clone);
           sub clone {
               my($proto) = @_;
               my $object = data_clone($proto);
               $object->do_something();
               return $object;
           }
           # ...

           # Bar is also clonable
           $o = Bar->new();
           $c = clone($o); # Bar::clone() is called

DESCRIPTION

       "Data::Clone" does data cloning, i.e. copies things recursively. This is smart so that it
       works with not only non-blessed references, but also with blessed references (i.e.
       objects). When "clone()" finds an object, it calls a "clone" method of the object if the
       object has a "clone", otherwise it makes a surface copy of the object. That is, this
       module does polymorphic data cloning.

       Although there are several modules on CPAN which can clone data, this module has a
       different cloning policy from almost all of them.  See "Cloning policy" and "Comparison to
       other cloning modules" for details.

   Cloning policy
       A cloning policy is a rule that how a cloning routine copies data. Here is the cloning
       policy of "Data::Clone".

       Non-reference values

       Non-reference values are copied normally, which will drop their magics.

       Scalar references

       Scalar references including references to other types of references are not copied deeply.
       They are copied on surface because it is typically used to refer to something unique,
       namely global variables or magical variables.

       Array references

       Array references are copied deeply. The cloning policy is applied to each value
       recursively.

       Hash references

       Hash references are copied deeply. The cloning policy is applied to each value
       recursively.

       Glob, IO and Code references

       These references are not copied deeply. They are copied on surface.

       Blessed references (objects)

       Blessed references are not copied deeply by default, because objects might have external
       resources which "Data::Clone" could not deal with.  They will be copied deeply only if
       "Data::Clone" knows they are clonable, i.e. they have a "clone" method.

       If you want to make an object clonable, you can use the "clone()" function as a method:

           package Your::Class;
           use Data::Clone;

           # ...
           my $your_class = Your::Class->new();

           my $c = clone($your_object); # $your_object->clone() will be called

       Or you can import "data_clone()" function to define your custom clone method:

           package Your::Class;
           use Data::Clone qw(data_clone);

           sub clone {
               my($proto) = @_;
               my $object = data_clone($proto);
               # anything what you want
               return $object;
           }

       Of course, you can use "Clone::clone()", "Storable::dclone()", and/or anything you want as
       an implementation of "clone" methods.

   Comparison to other cloning modules
       There are modules which does data cloning.

       "Storable" is a standard module which can clone data with "dclone()".  It has a different
       cloning policy from "Data::Clone". By default it tries to make a deep copy of all the data
       including blessed references, but you can change its behaviour with specific hook methods.

       "Clone" is a well-known cloning module, but it does not polymorphic cloning. This makes a
       deep copy of data regardless of its types. Moreover, there is no way to change its
       behaviour, so this is useful only for data which link to no external resources.

       "Data::Clone" makes a deep copy of data only if it knows that the data are clonable. You
       can change its behaviour simply by defining "clone" methods.  It also exceeds "Storable"
       and "Clone" in performance.

INTERFACE

   Exported functions
       clone(Scalar)

       Returns a copy of Scalar.

   Exportable functions
       data_clone(Scalar)

       Returns a copy of Scalar.

       The same as "clone()". Provided for custom clone methods.

       is_cloning()

       Returns true inside the "clone()" function, false otherwise.

DEPENDENCIES

       Perl 5.8.1 or later, and a C compiler.

BUGS

       No bugs have been reported.

       Please report any bugs or feature requests to the author.

SEE ALSO

       Storable

       Clone

AUTHOR

       Goro Fuji (gfx) <gfuji(at)cpan.org>

LICENSE AND COPYRIGHT

       Copyright (c) 2010, Goro Fuji (gfx). All rights reserved.

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