Re: Re: Objects with varying classes

Thanks, I'm starting to get the picture! I'll dig through the links in that
ticket and see if I can learn something more.

Cheers,

Manuel

On Wed, 26 Sep 2018 at 16:42, Jason Madden <[email protected]>
wrote:

> In general, the only way to change the `__class__` of a Persistent object
> is to update *all* references to it. For references in a BTree, that may
> mean updating the tree itself (if small) or the individual bucket. There's
> further discussion of this here:
> https://github.com/zopefoundation/BTrees/issues/72
>
> Because finding and changing all references is usually difficult (even one
> missed reference can break everything), this is not usually recommended for
> applications (migration tools can be written to do this by crawling through
> the entire database object-by-object, but that's rarely practical for an
> application). This is one way that interfaces can be more useful than
> classes: dynamically changing the interfaces an object provides with
> `interface.alsoProvides(object, IFoo)` or
> `interface.noLongerProvides(object, IFoo)` propagates automatically to all
> references to the object.
>
> HTH,
> Jason
>
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