Re: Get child model class
This might work: http://docs.python.org/library/functions.html#isinstance -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
I now the isinstance function but that will return the CF class. I want to know the child class of CF for that specific primary key. On May 6, 9:30 pm, Shawn Milochik wrote: > This might work: > > http://docs.python.org/library/functions.html#isinstance -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
On 05/06/2011 03:32 PM, pbzRPA wrote: I now the isinstance function but that will return the CF class. I want to know the child class of CF for that specific primary key. The isinstance function doesn't return a class. It returns a boolean, based on the class(es) you are inquiring about. You could also try these: instance._meta.module_name instance._meta.db_table These only return strings, but they'll get you the info you're looking for. -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
Just to clarify your suggestion In [100]: isinstance(x, CFT) Out[100]: False In [101]: isinstance(x, CFI) Out[101]: False In [105]: isinstance(e, CF) Out[105]: True This is not what I am looking for. I want to know to what class the CF primary key points to. So if it's CFT or CFI -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
Is your CF base class an abstract base class[1]? If it's not, then your
database actually has separate tables for CF, CFI and CFT .. and when you
access a `doc.cf` you're really getting the CF model instance, *not* the
derived class instance.
IIRC if you make CF an abstract base class then this will work the way you
want -- accessing doc.cf will return an instance of the appropriate derived
class.
Alternatively, if you want to keep the multi-table setup, you can try to get
each derived class instance from the base class, as described here[2] ("If
you have a Place that is also a Restaurant...") -- like:
{{{
x = doc.cf.all()[0]
try:
x = x.cfi
x_is_a_CFI = True
x_is_a_CFT = False
except CFI.DoesNotExist:
try:
x = x.cft
x_is_a_CFT = True
x_is_a_CFI = False
except CFT.DoesNotExist:
# x is neither a CFI nor a CFT
}}}
[1]
http://docs.djangoproject.com/en/dev/topics/db/models/#abstract-base-classes
[2]
http://docs.djangoproject.com/en/dev/topics/db/models/#multi-table-inheritance
On Fri, May 6, 2011 at 3:41 PM, pbzRPA wrote:
> Just to clarify your suggestion
>
> In [100]: isinstance(x, CFT)
> Out[100]: False
>
> In [101]: isinstance(x, CFI)
> Out[101]: False
>
> In [105]: isinstance(e, CF)
> Out[105]: True
>
> This is not what I am looking for.
>
> I want to know to what class the CF primary key points to. So if it's
> CFT or CFI
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To post to this group, send email to django-users@googlegroups.com.
> To unsubscribe from this group, send email to
> django-users+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/django-users?hl=en.
>
>
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Re: Get child model class
Thank you, this is more or less what I am looking for. I don't however want to make the CF class an abstract class as I want to have some common fields in there. The Idea behind this is that I want to store custom fields (CF) for various models that a user will be defining themselves. I do not want to keep the data in a single table as I want to be able to filter and do database actions on specific field types. But in order recreate a dynamic form from all the CF fields belonging to a document (Doc) I want to be able to iterate over Doc.cf.all() and add the specific CF field type to a form. I hope that makes sense :) -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
this is more or less what I found. I will have to see how I can implement it on my side. http://djangosnippets.org/snippets/1037/ -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
Re: Get child model class
Ok this solution worked for me :):)
{{{
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 CFManager(models.Manager):
def get_query_set(self):
return SubclassingQuerySet(self.model)
class CF(models.Model):
type = models.CharField(max_length = 40)
content_type =
models.ForeignKey(ContentType,editable=False,null=True)
objects = CFManager()
def save(self, *args, **kwargs):
if(not self.content_type):
self.content_type =
ContentType.objects.get_for_model(self.__class__)
super(CF, self).save(*args, **kwargs)
def as_leaf_class(self):
content_type = self.content_type
model = content_type.model_class()
if (model == CF):
return self
return model.objects.get(id=self.id)
class CFT(CF):
data = models.CharField(max_length=20)
objects = CFManager()
class CFI(CF):
data = models.IntegerField()
objects = CFManager()
class Doc(models.Model):
name = models.CharField(max_length = 40)
cf = models.ManyToManyField(CF, null = True)
}}}
now when I do:
In [12]: doc.cf.all()
Out[12]: [, ]
Thanks for all the suggestions and help.
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