[Newbies] 'locking' an object

[Marcin Tustin]

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 <merlyn at stonehenge.com> wrote:
>
> >>>>> "Sean" == Sean Allen <sean at monkeysnatchbanana.com> 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
> <merlyn at stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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> See http://methodsandmessages.vox.com/ for Smalltalk and Seaside
> discussion
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