#9318: "Virtual" behaviour for signal dispatcher and model inheritance
-------------------------------------+--------------------------------------
Reporter: svetlyak40wt | Owner: nobody
Status: new | Milestone:
Component: Core framework | Version: 1.0
Resolution: | Keywords: model inheritance,
signals, dispatch
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by mtredinnick):
* needs_better_patch: => 0
* stage: Unreviewed => Accepted
* needs_tests: => 0
* needs_docs: => 0
Comment:
The principle seems sound enough, although we need to think hard about
whether to turn this on by default, since it will change existing
behaviour in backwards-incompatible ways for some signal handlers. It
could be controlled in an "off by default" way by adding a flag to the
connect method, indicating that we also wish to receive emits that
originated on the child. We should consider adding a parameter like
"from_child" to signal emits to indicate if the signal is coming from a
sub-class so that handlers have an opportunity to avoid duplicate work.
On an implementation note (and the patch needs more careful examination
than I've given it just now, but this stood out), if we're going to "leak"
information about `_meta` and parents into dispatcher.py, we might as well
just test if it's an instance of `django.db.models.Model`, rather than
seeing if it's a class with a `_meta` attribute. But there could be some
other way to structure that entirely so that working out the right
emitting classes to use can be more self-contained within a model itself
and the dispatcher.py could avoid knowing about that. Needs some
thought/creativity.
I'll make this "accepted", since it's a feature worth adding, but what
shape the final feature will take still needs a bit of consideration, I
feel.
--
Ticket URL: <http://code.djangoproject.com/ticket/9318#comment:1>
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