On 08/25/2016 07:50 AM, Torsten Landschoff wrote:
Hi Mike,

On Wednesday, August 24, 2016 at 1:27:42 PM UTC+2, Mike Bayer wrote:


    if you've already solved the problem I'd rather not get into it :)


I am still curious about the inner workins of the DependencyProcessors
of sqlalchemy and how it would be possible to implement a custom
relationship property.
Not that I would make use of it currently. :-)


well dependencyprocessor is about doing the objects in the right order, and about invoking a command to "sync" important attributes from one side to the other, which means copying the PK of one object to the FK of another. I guess in this case we'd be "copying" the PK of related objects into the local object's comma-separated list of keys. From that perspective this is not much of a "DependencyProcessor" problem because you have this local attribute that just contains a view (comma-separated-list of keys) of a collection attribute on the same object. That is, I don't see much of a "topological" problem here if I'm understanding correctly. Copy-on-write is done by an attribute event, object is written therefore we set a flag, in before_flush() we copy all the objects that need to be copied-on-write, then I think you have the after_flush there to update the parent object. you can set up Bundle.members there also.


Greetings, Torsten

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