Question

Consider the following code:

package Test1;
use Moose; 

has 'something' => (
    is => 'rw',
    default => 'BLAH!'
);

sub printSomething {
    my ($self) = @_;
    ## What should I use here to get the value of something?
    print $self->something;
}

package Test2;

Test1->printSomething();

How can printSomething access something?

Answer 1

It can’t. You have to instantiate a Test1 object in order for attribute defaults to be constructed. They don’t hang out in the class.

If you want true class attributes in Moose, you can just write a method that closes over something and returns it:

{
    my $class_attr = 'BLAH!';
    sub something { 
        return $class_attr;
    }
}

Of course, then you have to do some more work to add setters and clearers and whatnot, if you need those. A better way is to use MooseX::ClassAttribute like this:

package Test1;

use Moose;
use MooseX::ClassAttribute;

class_has 'something' => ( 
    is       => 'rw',
    default  => 'BLAH!'
);

That has the advantage of making Moose aware of your class attribute, and adding in meta-introspection goodness automatically.