Hi all,
I have a situation here where I do not know how to use
the filter() function in the database API to obtain a
QuerySet. I am describing the schema and what I have
done, below. I hope you have an answer to my question.
# Only the necessary fields are shown here
class A(models.Model):
pass
class B(models.Model):
a = models.ForeignKey(A)
status = models.IntegerField('Status', blank=False)
date = models.DateField('Date', blank=False)
class Meta:
get_latest_by = 'date'
Whenever there is a change in the status of a row in
table A, a new row is added to table B, to reflect that
change. The latest row in table B corresponding to an
A, represents the current status of that A. It is
possible that there exists an A, which has no entry in
table B.
Now, what I want is a QuerySet of A's whose current
status is 1.
As of now, this is what I am doing:
class ValidAsManager(models.Manager):
"""does not return a QuerySet"""
def get_query_set(self):
return (i for i in super(ValidAsManager, self).get_query_set()
if i.status() == 1)
class A(models.Model):
objects = models.Manager()
current_objects = ValidAsManager()
def status(self):
try:
s = self.b_set.latest()
return s.status
except ObjectDoesNotExist:
return 0
I am not able to use generic views for listing the
valid A's because ValidAsManager does not return a
QuerySet. Could someone tell me what I can do to return
a QuerySet? How can I use the filter function to do so?
If you feel my schema is incorrect, I can consider
changing it.
Thanks,
Suriya
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