Problem with Meta inner class accessing its parent
Kevin Renskers
I am having a bit of a problem. I have a model with 3 name fields,
each for a different language. By creating an __unicode__ function
like below, I always get the correct name for the current language.
Works fine.
But, I want to change the default ordering for this model, so that in
each language, the correct order is used. Sadly, this doesn't work, as
I get the error "NameError: name 'Substrate' is not defined". Also
"self" and "super" don't seem to work. I just can't seem to be able to
access the parent class from within the Meta class.
I can't even repeat the getLanguage function into the Meta class,
because then I get an the error "TypeError: 'class Meta' got invalid
attribute(s): getLanguage".
class Substrate(models.Model):
name_en = models.CharField(max_length=255)
name_de = models.CharField(max_length=255, blank=True)
name_nl = models.CharField(max_length=255, blank=True)
def getLanguage(self):
from django.utils import translation
current_language = translation.get_language()
if not current_language:
current_language = 'en'
return current_language
def getName(self):
current_language = self.getLanguage()
name = getattr(self, 'name_'+current_language, self.name_en)
if not name:
name = self.name_en
return name
def __unicode__(self):
return self.getName()
class Meta:
ordering = [('name_%s' % Substrate.getLanguage()), 'name_en']
If anyone has an idea how on to do this, I would be very happy.
Thanks!
Cheers,
Kevin
Bill Freeman
that at the time
you try to set the value of Meta.ordering, class Substrate does not yet exist.
You can dig into the Substrate.objects._meta later to add ordering, probably.
Your design wouldn't have worked anyway, since getLanguage would only
have been called once, at import time, and even if that worked, it wouldn't
follow current language as it changes (I presume) from request to request.
Oh, and since you're not calling getLanguage on a class instance, it would
have to be declared a staticmethod or classmethod, and not get the self
argument or replace it with cls (for classmethod). Static method would be
the choice here (and no self)
It's mildly possible that ordering is allowed to be a callable. If
so, you could
assign it to a function (not a method of the not yet defined Substrate). That's
the function itself, no parentheses. The function would return the list.
If ordering can't be a callable, you could create a class that implements enough
of list behavior to satisfy the framework (a subject for research or
experimentation,
but iteration might be enough) and set ordering to an instance, whose apparent
content depends on the current language.
It still might not work, if the __metaclass__ processes Meta.ordering at clas
definition time. You have the source code.
Bill
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Kevin Renskers
getLanguage design did seem to work though, as changing the language
did have an effect on the __unicode__ function: in the admin interface
the correct values (for that language) were shown. At least it did so
on the local runserver environment. I can see though that even though
__unicode__ is called every time, the ordering is probably called only
at import time, and my little plan won't work.
Have to find a solution for that problem first I guess, before I even
start to tackle the problem of how to set the ordering...
On Dec 18, 5:00 pm, Bill Freeman <ke1g...@gmail.com> wrote:
> I can't promise that it will do what you want, but your problem is
> that at the time
> you try to set the value of Meta.ordering, class Substrate does not yet exist.
> You can dig into the Substrate.objects._meta later to add ordering, probably.
>
> Your design wouldn't have worked anyway, since getLanguage would only
> have been called once, at import time, and even if that worked, it wouldn't
> follow current language as it changes (I presume) from request to request.
>
> Oh, and since you're not calling getLanguage on a class instance, it would
> have to be declared a staticmethod or classmethod, and not get the self
> argument or replace it with cls (for classmethod). Static method would be
> the choice here (and no self)
>
> It's mildly possible that ordering is allowed to be a callable. If
> so, you could
> assign it to a function (not a method of the not yet defined Substrate). That's
> the function itself, no parentheses. The function would return the list.
>
> If ordering can't be a callable, you could create a class that implements enough
> of list behavior to satisfy the framework (a subject for research or
> experimentation,
> but iteration might be enough) and set ordering to an instance, whose apparent
> content depends on the current language.
>
> It still might not work, if the __metaclass__ processes Meta.ordering at clas
> definition time. You have the source code.
>
> Bill
>