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Program Repair Shop

6

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

• I think there's a lesson in there somewhere

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