Isn't it contradicting that you guys use abstract classes because they are
more "evolvable" and then lock everything with "final" so things don't change
as easily?
[]s Gus
---------- Início da mensagem original -----------
De: [EMAIL PROTECTED]
Para: [email protected]
Cc:
Data: Sat, 16 Jul 2005 00:06:57 +0200
Assunto: Re: [Wicket-user] Why no page interface?
> i agree.
>
> When you have a IPage object there should be able to have multiply Page
> implementations.
> But this is not really possible because the internals of page are pretty
> importand for wicket to let it work
>
> If you have a full blown page with all kind of components on it. I don't
> think putting an other page implementation beneath it
> that does honor the complete interface will really render the page...
> So if that isn't possible what is the use?
>
> johan
>
>
> Eelco Hillenius wrote:
> > Hi,
> >
> > One /very/ important reason not to use interfaces in this case is
> > that: interfaces are hard to evolve. Interfaces have to be pretty darn
> > stable before even considering throwing them out in the public, as
> > there is no way (not without a tough fight at least) you can alter it
> > later on - even adding a new method will break all clients.
> >
> > Another reason not to use interfaces here is that there is so much
> > behaviour in here (in the pages and components), that it is very hard
> > to extract something usefull out of it. What would the interface of a
> > Page be? One of the good practices when making interfaces is that they
> > should be small. Having an interface like
> > http://jakarta.apache.org/tapestry/tapestry/apidocs/org/apache/tapestry/IPage.html
> > doesn't really display that. They can be large, like the collection
> > interfaces are, but they have to be really, really stable and consistent.
> >
> > Just to be sure, and as I didn't make this decision for Wicket I asked
> > Jonathan Locke (who is doing movie stuff now, and left the mailing
> > lists for some time) why he choose for interfaces. Here's a partial
> > transcript of our chat:
> >
> > [22:31] jonathan: i don't believe in big interfaces
> > [22:31] jonathan: no interface should be as large as Page
> > [22:32] jonathan: it's too fragile
> > [22:35] jonathan: abstract classes are evolvable
> > [22:36] jonathan: interfaces should always be a set of methods that
> > you cannot ever imagine extending
> > [22:36] jonathan: it encapsulates a very specific set of behaviors
> > [22:37] jonathan: everyone should feel free to create/extract his own
> > IPage interface for use with proxies
> > [22:38] jonathan: there's something fundamentally wrong with the way
> > that current OO languages try to wire things together with static
> > interfaces.
> > [22:39] jonathan: unless i'm missing something, this is really not a
> > problem with wicket
> > [22:40] jonathan: in fact i think it's a feature
> > [22:40] jonathan: interfaces are really most useful for things that
> > are truly pluggable
> > [22:43] jonathan: my ideal number of methods in an interface is 1
> > [22:43] jonathan: ;-)
> > [22:44] jonathan: 2 is okay in some cases
> > [22:44] jonathan: 3 often should be re-thought
> > [22:44] jonathan: the more methods you have, the more likely it is
> > that you've got a bad design
> >
> > So, it is a design decission not to work with interfaces. However, as
> > Jonathan stated, you could extract an interface, let your page class
> > implement it and off you go. Furthermore, I wonder what it is you want
> > to do with a proxy that you can't do by simply subclassing? Or AOP?
> >
> > As a final statement I'd like to add that a framework like Wicket is
> > very different from a business system, which could have tons of
> > business methods that must be pluggable. Though even in that case, I
> > think too that interfaces are overused/ get too much focus with some
> > of the current popular frameworks. Seems to be getting a knee-jerk
> > reaction instead of a design decision. But maybe that's just me.
> >
> > Regards,
> >
> > Eelco
> >
> >
> > Peter Veentjer - Anchor Men wrote:
> >
> >> I`m trying to add Spring annotations to the Page, but because there
> >> is no page interface and only a Page class (with final methods) it is
> >> not possible to create a proxy and therefor it is impossible to
> >> enhance objects. This is very inconvenient..
> >>
> >> Why are the components not designed from interfaces? Designing from
> >> interfaces is common oo practice.
> >>
> >>
> >>
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