How can I reference the object when building it with Perl's Class::Struct?

Question

I am new to object oriented Perl and i have to access member variable of same object in another subrutine of same object. Sample code is here :

use Class::Struct;

struct Breed =>
{
    name  => '$',
    cross => '$',
};

struct Cat =>
[
    name     => '$',
    kittens  => '@',
    markings => '%',
    breed    => 'Breed',
    breed2 => '$',

];

my $cat = Cat->new( name     => 'Socks',
                    kittens  => ['Monica', 'Kenneth'],
                    markings => { socks=>1, blaze=>"white" },
                    breed    => { name=>'short-hair', cross=>1 },
                    ** //breed2 => sub { return $cat->breed->name;}**

                  );

print "Once a cat called ", $cat->name, "\n";
**print "(which was a ", $cat->breed->name, ")\n";**
print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";

But i am not sure how to use that $cat->breed->name in subroutine for breed2 ? Can some one help me with this.

Answer 1

The problem in breed2 is that you are trying to refer to a variable that you haven't defined yet. It looks like it is the same name, but it's not the object you are creating. It's a bit of a chicken-and-egg problem.

I'm not so sure that you want an anonymous subroutine like that in that slot anyway. Are you just trying to shorten $cat->breed->name to $cat->breed2? You can start with undef in breed2 and change its value right after the constructor since you'll have the reference to the object then. However, even if you put a subroutine there, you have to dereference it:

my $cat = Cat->new( name     => 'Socks',
                    kittens  => ['Monica', 'Kenneth'],
                    markings => { socks=>1, blaze=>"white" },
                    breed    => { name=>'short-hair', cross=>1 },
                    breed2   => undef,

                  );
$cat->breed2( sub { $cat->breed->name } );

print "Once a cat called ", $cat->name, "\n";
print "(which was a ", $cat->breed2->(), ")\n";
print "had two kittens: ", join(' and ', @{$cat->kittens}), "\n";