Re: Domain TRAP

From: Dominik Gruntz <"Dominik>
Date: Sat, 15 Sep 2001 00:46:32 +0200

> If my understanding is correct, then I have hit a real limitation
> of the BlackBox design. Namely, it is not possible to display
> many views of the SAME model and to embed them in texts. The domain
> conflict HAS to occur, because a shallow copy of the model keeps
> its domain.
That's correct. You cannot have two views which live in different
domains to refer to the same model. Such a situation can be achieved,
but you get trap 22 upon externalization. This is the case with the current
version of BlackBox, but also with the old versions. In an early version
(probably still Oberon/F) WriteStore did not issue a trap but simply
stopped externalize at the domain boundaries. The consequence was,
that you got the trap upon internalization of the half externalized store.

One thing you can do is, to make a deep copy of the model
when you externalize the view and see, that the model is not
in the same domain (can be checked with Stores.Joined).

There is one exception to the above observation. If your view
is implemented as Control, then it can refer to its "model"
from any domain -- but in this case the model is not externalized
when the view is stored.

- Dominik


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Received on Fri Sep 14 2001 - 22:46:32 UTC

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