[Newbies] 'locking' an object

Bert Freudenberg bert at freudenbergs.de
Thu Oct 2 17:18:35 UTC 2008

Am 02.10.2008 um 08:50 schrieb Sean Allen:

> If you wanted to take a mutable object and make it immutable and be  
> able to go back again to mutable,
> how could you do that?

What is your use case?

> In particular the part that has me as a smalltalk beginner stumped  
> is how to disallow any messages
> that would result in a state change while still allowing messages  
> that only read state.
> Do you have to handle on a message by message basis? ( Eeek lots and  
> lots of work )
> Or is there something you could work into a superclass and use in  
> its descendents? ( ideal for what I need. )

Well, it's hardly a beginner's topic, but you could make your class  
use a modified compiler that protects instance variable assignment by  
the check of an "immutable" flag.

This is basically how Avi's WriteBarrier works.

- Bert -

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