HeadFirst: Welcome Decorator Pattern. We’ve heard that you’ve been a bit down on yourself lately? Decorator: Yes, I know the world sees me as the glamorous design pattern, but you know, I’ve got my share of problems just like everyone. HeadFirst: Can you perhaps share some of your troubles with us? Decorator: Sure. Well, you know
I’ve got the power to add flexibility to designs, that much is for
sure, but I also have a dark side. You see, I can sometimes add a lot
of small classes to a design and this occasionally results in a design
that’s less than straightforward for others to understand. HeadFirst: Can you give us an example? Decorator: Take the Java I/O
libraries. These are notoriously difficult for people to understand at
first. But if they just saw the classes as a set of wrappers around an
InputStream, life would be much easier. HeadFirst: That doesn’t sound so bad. You’re still a great pattern, and improving this is just a matter of public education, right? Decorator: There’s more, I’m
afraid. I’ve got typing problems: you see, people sometimes take a
piece of client code that relies on specific types and introduce
decorators without thinking through everything. Now, one great thing
about me is that you can usually insert decorators transparently and
the client never has to know it’s dealing with a decorator. But like I
said, some code is dependent on specific types and when you start
introducing decorators, boom! Bad things happen. HeadFirst: Well, I think
everyone understands that you have to be careful when inserting
decorators, I don’t think this is a reason to be too down on yourself. Decorator: I know, I try not to
be. I also have the problem that introducing decorators can increase
the complexity of the code needed to instantiate the component. Once
you’ve got decorators, you’ve got to not only instantiate the
component, but also wrap it with who knows how many decorators. HeadFirst: I’ll be interviewing the Factory and Builder patterns next week – I hear they can be very helpful with this? Decorator: That’s true; I should talk to those guys more often. HeadFirst: Well, we all think
you’re a great pattern for creating flexible designs and staying true
to the Open-Closed Principle, so keep your chin up and think positively! Decorator: I’ll do my best, thank you
posted @ 2006-04-07 14:31 Allen Young 阅读(206) 评论(0) 编辑
2006年4月7日