Re: Moose 'clone' Constructor

Note that there can't be a general cloning routine free to use in all the cases. Imagine each object has a temp file created somewhere - when cloning an object, do you want it to share the same file(handle)? What if each object registers itself to a static hash or a parent object, generates a unique ID, seeds a PRNG, etc?

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{   package MyObj;
    use Moose;

    has fh => (is => 'ro', builder => '_build_fh');

    sub _build_fh {
        my ($self) = @_;
        open my $fh, '>', "/tmp/$self" or die $!;
        return $fh
    }

    sub DEMOLISH {
        my ($self) = @_;
        close $self->fh;
        unlink "/tmp/$self";
    }
}

my $o = 'MyObj'->new;

{
    my $c = $o->meta->clone_object($o);
}

say { $o->fh } "Hello world!";  # say() on closed filehandle $fh
[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]

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Re^2: Moose 'clone' Constructor by kcott (Archbishop) on Jul 05, 2018 at 03:27 UTC
G'day choroba, ++ That's a very valid point; thanks for raising it. It even applies to the code I'm currently working with, which I paraphrased for this post as: `my $cloned_object = ref($existing_object)->new();` [download] As I indicated in the OP, I want an object that's of the same class as `$existing_object`, but I want default values (not whatever values `$existing_object` has). In fact, if I had taken `$existing_object`'s values, that would've broken my code in all sorts of interesting ways. — Ken	[reply] [d/l] [select]

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Re^2: Moose 'clone' Constructor
by kcott (Archbishop) on Jul 05, 2018 at 03:27 UTC

G'day choroba,

++ That's a very valid point; thanks for raising it. It even applies to the code I'm currently working with, which I paraphrased for this post as:

my $cloned_object = ref($existing_object)->new();
[download]

As I indicated in the OP, I want an object that's of the same class as $existing_object, but I want default values (not whatever values $existing_object has). In fact, if I had taken $existing_object's values, that would've broken my code in all sorts of interesting ways.

— Ken

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