[REBOL] Re: Hack
From: joel:neely:fedex at: 28-Dec-2001 17:50
Hi, again, Sunanda,
[SunandaDH--aol--com] wrote:
> On a related subject, I'd like a way to get the name of an object.
> Example:
>
> MyObject: make object! [a: 0 b: 0 c: 0]
> MyFunc MyObject
> ...
> MyFunc: func [obj [Object!]][
>
> if error? [obj/a] [
> Print [?? "is missing its 'a' variable"]
> ] ; if
> ] ;func
>
> where we replace the "??" with the magic hack to dereference obj
> into "MyObject".
>
If you really want your objects to have human-readable identities,
you can add that easily:
MyObject: make object! [ID: "George" a: 0 b: 0 c: 0]
MyFunc: func [obj [object!]]
[ if error? [obj/a]
[ print [obj/ID "is missing its 'a' member"]]
]
which also works in the more general, anonymous cases:
MyObjects: copy []
MyProto: make object! [ID: "none" a: 0 b: 0 c: 0]
repeat i 20
[ append MyObjects make MyProto [ID: join "obj-" i]]
foreach ob MyObjects [MyFunc ob]
for i 1 20 1 [MyFunc MyObjects/:i]
> ... for precise functional
> equivalence, I need to add in the check that Obj is an object.
>
Which demonstrates that:
1) REBOL really doesn't support the conventional view of objects
very well, since I don't have any way to use the function
argument spec to state that I only what a particular *kind*
of object...
2) Perhaps the problem could be solved by making sure that MYFUNC
never gets called on anything that wasn't created from an
appropriate prototype -- but that's a code design issue and
(see the previous point) not something that REBOL explicitly
supports with language mechanisms.
-jn-
