Joe Laughlin wrote:
> I have a class that represents an airplane.  This class
> has a bunch of data members: x/y/z positions, x/y/z
> velocities, pitches, rolls, etc.  What I did is let the
> user configure what different attributes the airplane had
> in a YAML config file, then have the airplane class read
> in that file and setup attr_accessors for each attribute
> in the file.
>
> I have another object (call it airplane_drawing) that is
> responsible for drawing this airplane on the screen.  It
> needs to have access to some of the attributes of the
> airplane, and it needs have some of its own attributes
> changed whenever airplane's attributes changes.
>
> What is the best way to get airplane_drawing to be
> notified whenever some attribute of airplane is changed?
> Should I have a thread (or similar) that checks the
> airplane object to see if anything's changed?
>
> I hope I've explained this well enough for people to
> understand... I feel like this is a fairly common thing
> to do, but I'm not sure of the best way to do it.
>
> Thanks,
> Joe

Aha!  Thanks for the response you guys.  I knew that there was a pattern
that would help me, but I just couldn't think of it.