In the Pier-Magma integration there are instances od PRContext whose #properties instance var could really use zeroing to nil, before it is ever persisted.
Ok, no problem. Ma object serialization provides a couple of mechanisms for doing this.
I had a look at asStorageObject, but this seems to need an object that has its own graph. I assume that this means that it is representable as a discrete entity, rather than as part of the overall objects graph.
Absolutely correct. It should be a discrete entity, it should not link to any object in the database graph.
A fine example of this is for persisting CompiledMethods. See MaCompiledMethodStorage.
My current solution is to ensure that my 'dangerous' object is always sent #magmaCopy before it is stored in the persistent model, and also ensure that it is always sent #magmaCopy before it is likely to be used.
You could also call #beforeSerializingAny:do: to nil out (or do whatever) to the PRContext. For an example, see MaObjectSerializer>>#setUpPreAndPostProcessing, where Magma's base code that calls #flushCache on any Color before serializing it.
To use this, you would simply need to call this on your sessions serializer:
mySession serializer beforeSerializingAny: #PRContext do: [ : aPRContext | aPRContext initializeProperties ]
If you need to do something after materializing, add the following:
; afterMaterializaingAny: #PRContext do: [ : aPRContext | "reset the properties" ]
If you can't restore the properties from the image then you need to use the storage-object to capture whatever you need to restore it.
Finally, for anny of this to work, you *must* implement:
maWantsPreSerialization ^ true
and
PRContext>>#maWantsPostMaterialization ^ true
- Chris
This doesnt seem like the most efficient way of doing things. I thought of using preSerialisation, but looking at the code it appears that the result of preserializing has to be the same object, it cant be a copy, otherwise it gets treated as a StorageObject.
At present it looks as though I can combine, copying my dangerous object, so as not to disturb the users of the dangerous properties, and using preserialisation to zap the properties before storing.
any advice would be appreciated.
Keith
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