ch15.021_prob_ex15.3

Perl Best Practices the source code

##############################################################################
## Example 15.3 (NOT RECOMMENDED) from Chapter 15 of "Perl Best Practices"  ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


#  Example 15-3. A constructor that also clones


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;

my %selector_of;
my %data_of;

sub new {
    my ($invocant, $arg_ref) = @_;
 
    # If method called on an object (i.e. a blessed reference)...
    if (ref $invocant) {
        # ...then build the argument list by copying the data from the object...
        $arg_ref = {
            selector => $selector_of{ident $invocant},
            data     => [ @{$data_of{ident $invocant} } ],
        }
    }
 
    # Work out the actual class name...
    my $class = ref($invocant)||$invocant;
 
    # Build the object...
    my $new_object = bless anon_scalar(), $class;
 
    # And initialize its attributes...
    $selector_of{ident $new_object} = $arg_ref->{selector};
    $data_of{ident $new_object}     = $arg_ref->{data};
 
    return $new_object;
}