CODEWITHSUNDEEP
perloopinheritancemoose
botchi09
botchi09

Reputation: 21

Perl, Moose - subclass is not inheriting methods of a superclass

I'm new to Perl and have been directed to Moose as the go to source for Perl OO but I am having some problems with making it work. Specifically, methods of the superclass do not seem to be inherited. To test this I have created three files which contain the following:

thingtest.pl

use strict;
use warnings;
require "thing_inherited.pm";
thing_inherited->hello();

thing.pm

package thing;

use strict;
use warnings;
use Moose;

sub hello
{
    print "poo";
}

sub bye
{
    print "naaaa";
}

1;

And finally, thing_inherited.pm

package thing_inherited;

use strict;
use warnings;
use Moose;

extends "thing";

sub hello
{
    bye();
}

1;

So what one would normally expect is for method bye to be inherited as part of the subclass but I am given this error instead...

Undefined subroutine &thing_inherited::bye called at thing_inherited.pm line 11.

Can anyone explain if I'm doing something wrong here? Thanks!

edit: In doing this I have come across another conundrum: calling a method in my base class from my superclass that has should have been overwritten by the superclass is not overwritten. Say I had 

sub whatever
{

    print "ignored";

}

in my base class and added 

whatever();

in my bye method, calling bye would not produce the overwritten result, only print "ignored".

Upvotes: 2

Views: 747

Answers (2)

Richard
Richard

Reputation: 36

Just a few fixes. thing.pm was fine, but see the changes to thingtest.pl and thing_inherited.pm.

thingtest.pl: need to instantiate the object before using it, then you can use the method

use thing_inherited;
use strict;
use warnings;

my $thing = thing_inherited->new();
$thing->hello();

thing_inherited.pm: since the hello method is calling a method in it's class, you need to tell it just that

package thing_inherited;
use strict;
use warnings;
use Moose;

extends "thing";

sub hello {
  my $self = shift;
  $self->bye();
  }

1;

Output:

$ perl thingtest.pl

naaaa$

Upvotes: 0

ikegami
ikegami

Reputation: 385897

You have a function call, not a method call. Inheritance only applies to classes and objects, i.e. method calls. A method call looks like $object->method or $class->method. 

sub hello
{
    my ($self) = @_;
    $self->bye();
}

By the way, require "thing_inherited.pm"; should be use thing_inherited;

Upvotes: 7

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