[Seaside-dev] basicNew

[Avi Bryant]

On Mon, Sep 29, 2008 at 12:59 PM, Randal L. Schwartz
<merlyn at stonehenge.com> wrote:
>>>>>> "Avi" == Avi Bryant <avi at dabbledb.com> writes:
>
> Avi> Assuming no other changes to my code, this means that super's
> Avi> initialize is not called when you use the #x:y: or #point: class side
> Avi> creation methods, but *only* when you use a bare #new.
>
> Well, that's why you don't call basicNew unless you really mean it.
>
> The problem is that you need to decide if you're doing it the Squeak
> way or not.
>
> What I described in my earlier post is the Squeak way, and the way
> I learned looking at the Smalltalk image in 1981.  If you want to
> do it the Objective C way, be prepared for some incompatibility.

Ok, I'm still looking for a *complete* example of the "Squeak way",
and none of your posts so far provide one, so let me set up a straw
man and you can tell me where it's wrong.

WAPoint class>>x: xNumber y: yNumber
  ^ self new x: aNumber y: aNumber

WAPoint>>x: aNumber y: yNumber
   x := aNumber.
   y := aNumber

WAPoint>>initialize
  super initialize.
  self x: 0 y: 0

The only interesting/contentious part of this, I think, is the very
last line, where #x:y: is sent from the overridden #initialize method.
 I believe you have to include it, because if you don't, then sending
"WAPoint new" ends up with an uninitialized instance (nil for x and
y).  If you do include it, however, you end up performing the
initialization twice - this is not a big deal when all you're doing is
assigning some instance variables, but you can certainly imagine cases
where doubly initializing an instance would be costly or incorrect.
That's why I don't like this approach, but if I've misunderstood it,
let me know.

Here's the alternative I'm proposing again, for reference:

WAPoint class>>x: xNumber y: yNumber
  ^ self basicNew x: aNumber y: aNumber

WAPoint>>x: aNumber y: yNumber
   super initialize.
   x := aNumber.
   y := aNumber

WAPoint>>initialize
  self x: 0 y: 0

This way, whether you use #x:y: or #new, you end up initializing the
instance exactly once - and I'm still unclear on what the concrete
disadvantages are.

Avi