Am 02.10.2008 um 10:17 schrieb Sean Allen:
You'd have to specially code each accessor in that case to check the
flag.
Ideally I'd like to be able to step in front of every message send
to descendent objects and
decide whether to pass along ( read call ) or reject ( write call ).
then, all the logic is in one place and the accessors don't need to
know about what is going on.
any way to do that?
The proxy Randal was suggesting can do that. It encapsulates an
object, and decides wether to pass on messages or not.
i'm ok with the primitive problem as i don't need real immutability.
just 'application level' immutability...
ideally, without special coding in every accessor method ( that
would get tedious very quickly ).
On Oct 2, 2008, at 12:47 PM, Marcin Tustin wrote:
Surely if you have a wrapper class which only holds a reference to
a single object that has all of the data, and that has accessors,
then the wrapper can only use the accessors? The data object could
have a flag that causes all of the accessors to throw an exception
when it is set.
Or am I missing something?
On 10/2/08, Randal L. Schwartz <[EMAIL PROTECTED]> wrote: >>>>>
"Sean" == Sean Allen <[EMAIL PROTECTED]> writes:
Sean> If you wanted to take a mutable object and make it immutable
and be able
Sean> to go back again to mutable, how could you do that?
Squeak doesn't have that sort of capability. The immutability of a
few
classes is because the VM recognizes them specially, and not
available
at the programmer level without modifying the VM.
Other Smalltalk VMs are different. I think both VisualWorks and
GemStone/S
have primitive bits on an object to be informed when a mutation
might be
attempted.
You can simulate that *mostly* in Squeak by using a "proxy" object
that
intercepts all messages and looks for the dangerous ones, but
that's gonna be
a bit hard to do, and won't be aware of any new code that might
call the
mutating primitives directly. (*Any* method can call a primitive.)
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503
777 0095
<[EMAIL PROTECTED]> <URL:http://www.stonehenge.com/merlyn/>
Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc.
See http://methodsandmessages.vox.com/ for Smalltalk and Seaside
discussion
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