Now I have revise the code as follow:
The as_leaf_class():
def as_leaf_class(self):
content_type = self.content_type
model = content_type.model_class()
if (model == Product):
return self
try:
obj = model.objects.get(id=self.id)
return obj
except:
return None
#return model.objects.get(id=self.id)
The __iter__() and __getitem__():
def __getitem__(self, k):
result = super(SubclassingQuerySet, self).__getitem__(k)
if isinstance(result, models.Model):
alc = result.as_leaf_class()
if alc:
return alc
#return result.as_leaf_class()
else:
return result
def __iter__(self):
for item in super(SubclassingQuerySet, self).__iter__():
alc = item.as_leaf_class()
if alc:
yield item.as_leaf_class()
Is this solution correct?
On Apr 4, 8:19 pm, TTear1943 <1943....@gmail.com> wrote:
> I use a snippet inhttp://www.djangosnippets.org/snippets/1034/for my
> Model inheritance. It works fine at the first.However, after I delete
> some elements in database, the code works wrong.
> As I debug, I found that the problem resides in the method:
> as_leaf_class.
> In the following code:
> def as_leaf_class(self):
> content_type = self.content_type
> model = content_type.model_class()
> (1*) if(model == Contact):
> return self
> (2*) return model.objects.get(id=self.id)
> when query a deleted object, line (1*) will be False, So it tries to
> run line (2*) which raise an exception from get()
> Anyone could give a solution for this?
>
> The snippets I use is following:
> Model inheritance with content type and inheritance-aware manager
> from django.db import models
> from django.contrib.contenttypes.models import ContentType
> from django.db.models.query import QuerySet
>
> class SubclassingQuerySet(QuerySet):
> def __getitem__(self, k):
> result = super(SubclassingQuerySet, self).__getitem__(k)
> if isinstance(result, models.Model) :
> return result.as_leaf_class()
> else :
> return result
> def __iter__(self):
> for item in super(SubclassingQuerySet, self).__iter__():
> yield item.as_leaf_class()
>
> class MealManager(models.Manager):
> def get_query_set(self):
> return SubclassingQuerySet(self.model)
>
> class Meal (models.Model) :
> name = models.TextField(max_length=100)
> content_type = models.ForeignKey
> (ContentType,editable=False,null=True)
> objects = MealManager()
>
> def save(self, *args, **kwargs):
> if(not self.content_type):
> self.content_type = ContentType.objects.get_for_model
> (self.__class__)
> super(Meal, self).save(*args, **kwargs)
>
> def as_leaf_class(self):
> content_type = self.content_type
> model = content_type.model_class()
> if (model == Meal):
> return self
> return model.objects.get(id=self.id)
>
> class Salad (Meal) :
> too_leafy = models.BooleanField(default=False)
> objects = MealManager()
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