Re: Object-oriented thinking in SQL context?
Date: Wed, 17 Jun 2009 21:26:27 -0700 (PDT)
On Jun 17, 9:06 am, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> Marshall wrote:
> > On Jun 17, 4:45 am, "Nilone" <nil..._at_mega.co.za> wrote:
> >>"Bob Badour" <bbad..._at_pei.sympatico.ca> wrote in message
> >>>>Think 'class' ~ 'relation' (table)
> >>>But that would not only be a blunder but a great blunder.
> >>I'd like to clarify this for anyone coming from the OO side. If you map
> >>class to relation, you're breaking the OO rule of encapsulation and reducing
> >>the class to a simple aggregate type (struct). Presumably, you chose an
> >>encapsulated, polymorphic abstraction device for a reason, or did you do so
> >>just because you (or somebody at your company) read Lhotka's book? Classes
> >>map to domains (types) in the relation model, but be aware that subclassing
> >>is NOT subtyping.
> > Speaking just for myself, when I am programming in an OO language,
> > I map classes to whatever I feel like. OO really only provides the
> > one unit of abstraction, the class. If the only tool you have is a
> > class, everything looks like an object. Or something.
> > In other words, when I want an abstraction for something in
> > Java, I make it a class, because that's about the only choice.
> Does Java have no arrays or associative arrays?
Java has primitive arrays. They are sufficiently lame that I don't use them much. They also aren't all that pretty as far as the type system goes; Java array types are covariant but of course array-element-assignment is contravariant, so you can get (runtime) errors.
Java has a bajillion collection classes, and as such things go, they're actually pretty good. (Incl. dictionaries.) They are all class based. Java really, really wants you to use classes. (The anthropomorphism there is all in my phrasing; what I mean is that the language design makes the use of classes easy and doesn't provide much else to use.)
Marshall Received on Thu Jun 18 2009 - 06:26:27 CEST