Scribit Ian Eslick dies 23/04/2007 hora 18:55: > I'm not sure that deserializing a persistent object without actually > creating it would make much sense. What would you return from the > deserializer? What operations would it need to support?
I tend to think that deserialization should be something like deserialize-instance (which I'll call d-i for short), and be a member of the family of GFs whose system-supplied primary method calls shared-initialize, viz. initialize-instance, reinitialize-instance, update-instance-for-redefined-class, and update-instance-for-different-class. d-i should be a function with side-effects, that may take a placeholder instance and move it to an instance of the proper persistent class, with slots filled with either their transient value, their persistent value or a placeholder instance for the latter. > Think of it this way. If you get a value from a persistent index and > that value is a persistent object, then you want object identity, the > ability to inspect it's type, slot access, etc. The only way to do > that is to create something in memory which provides this. The only > way to that is to make sure your lisp has had the chance to construct > everything it needs via make-instance. I'm not sure make-instance should be called here. reinitialize-instance would be a far better choice. > Transient Slots: they have the semantics of ordinary lisp slots - you > cannot expect them to persist between images or after their > placeholder has been garbage collected. > Make-instance specializers: If you override the typical make-instance > via :before, :after, :around or specialized on your class, you have to > make sure that you predicate on :from-oid (this will be documented in > the new manual) to avoid resetting persistent values. Well, according to the spec, users should better define methods on make-instance, but on shared-initialize or initialize-instance. Curiously, Pierre -- [EMAIL PROTECTED] OpenPGP 0xD9D50D8A
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