I'm quite happy to see the topic is at least being considered! <3.
Although I suggested a solution, I like the solution posted by Collin in
the PR (I'd prefer solutions not involving signature changes in methods,
but anyway those signature changes Colin posted are not so... obtrusive).
I'd like to, however, propose a little change in Collin's code. Immediately
before this code in _add_items:
self.through(**dict(through_defaults, **{
'%s_id' % source_field_name:
self.related_val[0],
'%s_id' % target_field_name: obj_id,
}))
This one:
if callable(through_defaults):
through_defaults =
through_defaults(self.related_val[0], obj_id)
With these two lines, we could allow passing a callable to through_fields
(as we pass callables for defaults in django fields). The return value of
such callable should be a dictionary, while the arguments should be source
and target ids.
But even if this little change is not implemented, I like the Collin's
solution anyway.
Another subtopic to discuss is about enhancing the Collin's solution, is to
allow through_defaults be specified on field definition (In the same way we
define default values in... scalar... fields; I leave open the discussion
on whether such value should be overriden when using add, create, or any of
these methods as changed by Collin).
I like how this is going and hope that any solution (even if it is just the
as-is solution provided by Collin, with no changes) be accepted in any
near-future version <3.
El martes, 21 de marzo de 2017, 20:29:33 (UTC-5), Alex Hill escribió:
>
> Here's a little bit more historical discussion on the topic:
> *https://groups.google.com/d/topic/django-developers/uWe31AjzZX0/discussion
> <https://groups.google.com/d/topic/django-developers/uWe31AjzZX0/discussion>*
>
> On Wed, 22 Mar 2017 at 05:57 Russell Keith-Magee <rus...@keith-magee.com
> <javascript:>> wrote:
>
>> On Tue, Mar 21, 2017 at 2:37 PM, Adam Johnson <m...@adamj.eu
>> <javascript:>> wrote:
>>
>>> It does seem like a somewhat arbitrary historical restriction. Collin's
>>> PoC change is surprisingly small and simple.
>>>
>>> Seems like it would be fine if Django allowed add() and let any errors
>>>> about missing data bubble-up.
>>>>
>>>
>> As the person who *made* the “somewhat arbitrary historical restriction”…
>> :-)
>>
>> Honestly - the reason it was made was scope creep.
>>
>> I was trying to land Eric’s work on #6095, which was already moderately
>> complex. Nobody disagreed that adding an object to an m2m with a through
>> model was a *bad* idea - there were just a few design decisions that had to
>> be made. But if we made those decisions, #6095 was going to take *another*
>> couple of months to land; the perfect being the enemy of the good, we
>> decided to limit scope and land “simple” m2m add, and revisit the issue
>> later.
>>
>> I guess now is “later”… :-)
>>
>> Yours,
>> Russ Magee %-)
>>
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