Perl Hacks

Hack #44. Serialize Objects (Mostly) for Free

Store object data without mess, confusion, or big blobs of binary data.

Some programs really need persistent data, and sometimes mapping between objects and multiple tables in a fully-relational database is just too much work. This is especially true in cases where being able to edit data quickly and easily is important—there's no interface more comfortable than your favorite text editor [Hack #12].

Instead of hard-coding configuration in a program, wasting your precious youth creating the perfect database schema, or doing XML sit-ups, why not serialize your important object data to YAML?

The Hack

If you use hash-based objects, it's very easy to serialize the data—just make a copy of the hash and serialize it:

use YAML 'DumpFile';

sub serialize
{
    my ($object, $file) = @_;
    my %data            = %$object;
    DumpFile( $file, \\%data );
}

This assumes, of course, that $object is the object you want to serialize and $file is the path and file to which to save the object.

If you use inside out objects [Hack #43], you have a bit more work to do:

package Graphics::Drawable; { use Class::Std; my %coords_of :ATTR( :get<coords> :init_arg<coords> ); my %velocities_of :ATTR( :get<velocity> :init_arg<velocity> ); my %shapes_of :ATTR( :get<shape> :init_arg<shape> ); sub get_serializable_data { my $self = shift; my %data; for my $attribute (qw( coords velocity shape )) { my $method = 'get_' . $attribute; $data{ $attribute } = $self->$method( ); } return \\%data; ...