Questa sera ho partecipato alla chat sui Design Patterns
organizzata da Emanuele. E' stata molto interessante, un esperimento da
ripetere, la discussione era piuttosto fluida e le opinioni dei partecipanti
molto interessanti.
Ne approfitto per rettificare una mia affermazione su Vlissides e il
pattern Singleton: non era lui a proporne la rimozione dal liblro della
GoF, o quantomeno non ho più trovato sue affermazioni in merito nonostante ci
siano suoi scritti critici in merito, la mia convinzione veniva da un'errata
associazione di idee con un vecchio post di Fowler sul suo blog (commento
all'OOPSLA2004, http://www.martinfowler.com/bliki/OOPSLA2004.html),
che riporto, dal quale si evince che Singleton è in generale considerato da
molti come un pattern da rimuovere tra la lista di quelli "buoni":
Before the beginning of the conference proper I attended a workshop on
reappraising the GoF book, ten years after it came out. ...
We did a number of discussions around the what next theme, perhaps the
most interesting one to report was an exercise in considering some to 'vote off
the island'. People voted on the patterns to indicate which ones they felt
needed deletion in the current form.
Four patterns were voted off. Factory Method (due to the confusion over
what it means - the pattern is different to the more common usage of the term),
Bridge, Flyweight, and Interpreter. Two patterns, Singleton and Chain of
Responsibility, were split decisions.
I found the votes and discussions interesting. Of course it's hard to
really consider this without looking at alternatives. I was surprised that
Singleton got away with a split decision, considering how unpopular it's become
amongst my friends. Most of the others were voted off because people felt
they were sufficiently uncommon and that other patterns would probably take
their place, sadly we didn't have time to consider new members.
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