Second try. I promise there won't be a third.
Is there a rationale for multiple managers per model? Or is it a
that's-how-it's-always-been thing?
If I missed something obvious, I would have received a "wrong list or
rtfm" reply by now, supposedly.
{{{
class AManager(Manager):
pass
class BManager(Manager):
pass
class A(Model):
a_objects = AManager()
class Meta:
abstract = True
class B(Model):
b_objects = BManager()
class Meta:
abstract = True
class C(A,B):
objects = Manager()
class D(B,A):
objects = Manager()
}}}
Now C._default_manager == C.a_objects and D._default_manager ==
D.a_objects.
If A and B come from different modules _default_manager will be
picked depending on import order.
If this is by design, I'd be happy with a "wontfix" reply. I'm not
using multiple managers anyway.
[1] http://code.djangoproject.com/ticket/7154
Am 31.05.2008 um 19:16 schrieb Johannes Dollinger:
>
> I'd like to propose a change of the Model.defaul_manager concept. My
> first concern was the inability to control the default_manager when
> subclassing a Model that already provides a default_manager (the base
> class' manager will be added before the subclass' manager).
>
> This could be solved by either an explicit default_manager
> declaration in Meta,
>
> my_manager = MyManager()
> class Meta:
> default_manager = 'my_manager'
>
> or the convention that default_managers are called `objects` (then
> you wouldn't even need the default_manager concept).
> I strongly favour the latter, because it's dry and simple. Yet it's a
> backwards incompatible change ..
>
> My attempts to come up with a good example to illustrate my proposal
> were in vain - and I begin to think, that it's always cleaner to keep
> a single Manager (and subclass as necessary) and never ever alter
> Manager.get_query_set() behaviour (or all() for that matter). Does
> anybody have a good use-case that depends on multiple managers?
>
> Here is how I would write the custom manager doc example (from [1]):
> http://dpaste.com/53948/ (Those proxy methods could use a little meta-
> programming.).
>
> Has this approach any flaws? If not, shouldn't the docs advertise
> this more flexible approach instead of multiple Managers?
>
> ___
> Johannes
>
> [1] http://www.djangoproject.com/documentation/model-api/#custom-
> managers
>
>
> >
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