I'm trying to get 'super' to work in a prototype-based OO system and currently have this ugly mess. I'm wondering if there is a better way.

The system uses hash-based objects which can have CODE ref entries which are run to provide per-object behaviour. It has single inheritence so 'super' is not too complicated. I hope the intent is clear without all the entire class.

The ideal solution would have 'super' know which code ref called it and then find the next in the object_can_all list. Next best would be a syntactic improvement to make the second form below easier. Ideas? Suggestions? 

=item super

Call the prototype's/parent's version of a function.

This is tricky because the when coding the $self->super call intends
to target one thing but a subclass of this will provide a different
$self that has the original as it's prototype.  So super needs to
discover when this has happened, seemingly impossible using just
caller($n) and $self.  More information is needed from 'new' time.
That's why there's two interface variants:

    $self->super(check => @_);

This asserts that there are only two "check" routines in the prototype
chain for $self and it calls the last one (which assumes that 
only the first/sub-object uses super).

The second variant requires a more complex declaration, permitting
more than two subs in a hierarchy.  You must pass super a coderef
to the surrounding code so that it can find it in the list of
potential versions.

    use WeakRef;
    my $this_sub;
    $this_sub = sub {
        my $self = shift;
        $self->super($this_sub, check => @_);
    }
    $object->{check} = $this_sub;
    weaken $this_sub;

The weaken is important to avoid a circular reference as the closure
captures $start_code_ref.

This interface division means that objects must use the second

form if they want to their sub-objects to be able to override
a method using super.  Requiring adjustments to the parent is
ugly but seems to be the only solution.

Devel::Caller provides caller_cx which would help but it is seems flak
+y.

=cut

sub super { 
    if(ref $_[1] ne 'CODE') {

        # No code ref, super must be unambiguous
        my ($self, $attr) = (shift, shift);

        # Find all versions of $attr for this object
        my @subs = $self->object_can_all($attr);

        die "Ambiguous super call for $attr on $self" if @subs != 2;

        # Super must be intended for the second (ie. last) one
        my $super_sub = pop @subs;
        return $self->$super_sub(@_);

    } else {

        # They gave us a reference to the intended start sub
        my ($self, $this_sub, $attr) = (shift, shift, shift);

        # Find where $this_sub is
        my @subs = $self->object_can_all($attr);
        my $n = 0;
        while ($subs[$n] != $this_sub) { $n++ }

        # Run the next highest one
        die "No super for $attr on $self" unless exists $subs[$n+1];
        my $super_sub = $subs[$n+1];
        return $self->$super_sub(@_);

    }
}

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In reply to Sub getting it's own CODE ref? Proto-OO by bsb

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