Destructors

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(Hat tip to Damian for prompting me on this. I had been meaning to get around to it, but he was kind enough to provide me with the background. Heck, I could have just cut-n-pasted his email)

Just as we have constructors, we also need destructors. These are special methods called during object destruction to ensure that everything that needs to be cleaned up/finalized, is cleaned up/finalized.

Core Perl has an issue here:

#!/usr/bin/env perl
use Less::Boilerplate; # personal version of Modern::Perl

package Parent {
    sub new       { bless {} => shift }
    sub inherited { say "Inherited" }
    sub DESTROY   { say "Parent" }
}

package Child {
    our @ISA = 'Parent';
    sub new     { bless {} => shift }
    sub DESTROY { say "Child" }
}

{
    my $thing = Child->new;
    $thing->inherited;
}

say "Done";

Running that prints:

Inherited
Child
Done

Note that Parent is not printed because the parent destructor is not called. Thus, you need to call $self->next::method at the end of every DESTROY.

Moose has sane object destruction via DEMOLISH, but Cor ain't Moose. Moose has BUILD and DEMOLISH for construction/destruction, so Cor should have CONSTRUCT and DESTRUCT for its object construction/destruction.

Most of the time you won't need a DESTRUCT method.

method DESTRUCT ($is_global_destruction) {
    if ($is_global_destruction) {
        ...
    }
    else {
        ...
    }
}