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.

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.