Re^6: Aspect-Oriented Programming: Couple of Short Examples

[adrianh]

I'm curious - how do you see Perl or C++ or Java lacking this behavior?

Because Perl, C++ and Java do not have metaclasses.

I know that my personal baseclass has the following lines in the new() call:

That's the difference. You have to add code to the new() call. In Python (or other languages with appropriate metaclass support) you don't have to change your baseclass's methods at all, you just say that your base class is implemented via a specific metaclass. The metaclass behaviour is completely separated from the object classes implementation.

For example, imagine that the behaviour we wanted to add to object initialisation was logging. Now imagine that our logging requirements change and we need to log all access to object mutators in addition to object initialisation. In a language without metaclasses we would have to add a method call to every mutator. With a metaclass you just have to change the way that mutators are implemented to include a call to the logging routines.