in reply to Re: perspective and object-disorientation
in thread perspective and object-disorientation

I see what you are saying. I think the Employee/Artist example i gave doesn't really hold up to what I was trying to express, but was more convenient than getting too contrived on a subject Im not 100% on. (not 25% on!)

So far I have been using a similar setup to what you suggest. Im not too clued-up on patterns, but it seems to be like the hasa relationship suggested by others?.
I find this kind of "orientation" simple to manage - it is DOM-ish and familiar. All objects inherit a common base-class for general introspection and delegation , then rely on their own class to provide their "individuality".

The problem i find with this, is that an objects "individuality" is purely based on its data - it is difficult to have dynamic behaviour, sensitive to both the environment the object is created in, and the relationship between (for example) caller() and $self at any given time.
If @ISA were an instance variable, then this could be realistically implemented. The class may provide a default - but time, context and environment could mutate it appropriately. As it stands, @ISA is per class, so the only way I can think of to hack it, would be something like 
sub callMethod
{
    my $self = shift;
    my ($method, @args) = @_;
    
    # pseudo-code only ;)
    (defined( $self->{buddies}->{ caller() } ) ) ?
            unshift @ISA, "Behaviour::Informal" :
            unshift @ISA, "Behaviour::Guarded" ;
            
    my @return = $self->$method(@args) if $self->can($method);
    
    # hide what we just did from the rest of our class!
    shift @ISA;
    return @return;
}

[download]

I realise the limitations with the above code, but i guess its somewhat less abstract than the pseudo-existential waffle of "perspectives" ;)
Im pretty much out of my depth here, so perhaps I am just thrashing in comp.sci terminology?

Replies are listed 'Best First'.
Re: Re: Re: perspective and object-disorientation
by pdcawley (Hermit) on Jan 19, 2003 at 22:32 UTC
    But caller doesn't do what you want. Try: 
    sub respond_to_message_from { 
  my $self = shift;
  my($message, $sender);
  
  my $attitude = $self->appropriate_attitude_to($sender);
  $attitude->respond_to_message_from($self, 
                                     $message, 
                                     $sender);
}

    [download]
    This avoids monkeying with @ISA, which can only be a good thing. $attitude is an example of the Strategy Pattern. Note that I've not got an @args parameter to this function, instead I'd expect them to be wrapped up in teh $message object (which can be thought of as an example of the Argument Object pattern.
[reply]
[d/l]
[select]
      ah!

      I realised the insufficiency of using caller() in that way - but your example is still great. Having the  $self->appropriate_attitude_to($sender) return an object is really...neat.

      Thanks, I'll play around with this
[reply]
[d/l]

In Section Meditations