Class::Observable

• Idea: Say that Alarm inherits from Class::Observable

• It then inherits two methods:

  • ->add_observer

  • ->notify_observers

• When it calls ->notify_observers, each observer's ->update method is called

  • An observer can be an object that supports an ->update method

  • It can also be the name of a class that supports an ->update method

  • It can also be a plain subroutine, which is invoked

     my $alarm = Alarm->new();  # Alarm inherits from Class::Observable
     my $guard  = Guard->new();

     $alarm->add_observer($guard);   # Inherited method

     ...

     $alarm->notify_observers(...);    # Inherited method
     # Calls $guard->update(...);

• Why not $guard->notify(...)?

  • I don't know