Re: object oriented Perl advice / constructor creation in child class

[kcott]

G'day smarthacker67,

While I assume you're just using "A", "B", etc. as examples, this generally isn't a good idea as you can run into name collisions; for instance, B.pm is a core module which you'll already have installed.

I don't understand where "C1.pm" sits in your hierarchy. It seems to be both a file and directory which is a subdirectory of another file ("C.pm"). Obviously that can't be the case but I don't know what you want: "lib/C/C1.pm"?, "lib/C1.pm"?, something else?

Here's some skeleton code to show how you might achieve this sort of thing with Moose. This is intended as an academic exercise: there's no suggestion that this is production-grade code; nor that Moose is the best choice for your specific application.

$ cat lib/A.pm 
package A;

use Moose;

has bar => (
    is  => 'rw',
    default => 'A-bar',
);

__PACKAGE__->meta->make_immutable;

$ cat lib/C.pm
package C;

use Moose;

sub whos_who {
    my ($self) = @_;

    print "whos_who() is in package: ", __PACKAGE__, "\n";
    print "\$self is in package: ", ref($self), "\n";

    return;
}

__PACKAGE__->meta->make_immutable;

$ cat lib/D.pm
package D;

use Moose;

has 'bar' => (
    is  => 'rw',
    default => 'D-bar',
);

__PACKAGE__->meta->make_immutable;

$ cat lib/C1.pm
package C1;

use Moose;

extends 'C';
use A;
use D;

has a => ( is => 'ro', default => sub { A->new } );
has d => ( is => 'ro', default => sub { D->new } );

sub foo {
    my ($self) = @_;

    print $self->a, "\n";
    print $self->a->bar, "\n";
    print $self->d, "\n";
    print $self->d->bar, "\n";
    $self->whos_who;

    return;
}

__PACKAGE__->meta->make_immutable;

$ cat ./acd.pl
#!/usr/bin/env perl

use strict;
use warnings;

use lib 'lib';

use C1;

my $c1 = C1::->new();

$c1->foo();

$ ./acd.pl
A=HASH(0x25db7c0)
A-bar
D=HASH(0x25db880)
D-bar
whos_who() is in package: C
$self is in package: C1

Update (typo fix): s{lib/C/C.pm}{lib/C/C1.pm}

[smarthacker67]

Hi Sir,

Thanks for this brief explanation I would definitely give a try.

dir structure looks like

lib/A.pm
lib/B.pm
lib/C.pm
lib/C/C1.pm
lib/D.pm

Wanted to achieve deep inheritance where object of C1 should inherit methods of A,B,C, & D

[kcott]

dir structure looks like

...
lib/B.pm
...
lib/C/C1.pm
...

lib/B.pm

As previously stated, B.pm will already exist on your system. Attempting to write new code with "package B;" will cause you all sorts of problems. You should avoid this name.

lib/C/C1.pm

That's fine. The class name will become "C::C1". My previously posted "lib/C1.pm" should be moved to "lib/C/C1.pm", and the first line should be changed to:

package C::C1;

In my "./acd.pl", you should change

use C1;

my $c1 = C1::->new();

to

use C::C1;

my $c1 = C::C1::->new();

After making those changes, note the difference in the last line:

$ ./acd.pl
A=HASH(0x9897d0)
A-bar
D=HASH(0x989890)
D-bar
whos_who() is in package: C
$self is in package: C::C1

The hexadecimal values in "X=HASH(0xhhhhhh)" will likely be different: that's not significant; you could get different values on separate runs using the same code.