django custom manager with filter parameter

问题

I would like to add a custom manager which can be called from a template, but does not affect the entire model (e.g. admin views) and which listens to a parameter set in the request (user_profile).

The following is what I have so far:

models.py:

class CurrentQuerySet(models.query.QuerySet):
    def current(self):
            return self.filter(id=1) ## this simplified filter test works..
class CurrentManager(models.Manager):
    use_for_related_fields = True
    def get_query_set(self):
            return CurrentQuerySet(self.model)
    def current(self, *args, **kwargs):
            return self.get_query_set().current(*args, **kwargs)

For model B is defined:

    objects = CurrentManager()

The template calls:

{% for b in a.b_set.current %}

But as soon as I try to pass a parameter to that filter (in this case a date stored on the user-profile) the method does not return any results.

e.g.:

models.py

class CurrentQuerySet(models.query.QuerySet):
    def current(self,my_date): 
            return self.filter(valid_from__lte=my_date) 

showA.html

{% for b in a.b_set.current(request.user.get_profile.my_date) %}

Instead of passing the parameter from the template, I have also tried to set this in the view.py

@login_required
def showA(request,a_id):
    my_date = request.user.get_profile().my_date
    a = A.objects.get(id=a_id)
    t = loader.get_template('myapp/showA.html')
    c = RequestContext(request,{'a':a,'my_date':my_date,})
    return HttpResponse(t.render(c))

Which part am I missing (or misunderstanding) here?

Thanks

R

Edit

Here the models. As mentioned, in this example it's a simple 1:n relationship, but can also be m:n in other cases.

class A(models.Model):
    #objects = CurrentManager()
    a = models.CharField(max_length=200)
    description = models.TextField(null=True,blank=True)
    valid_from = models.DateField('valid from')
    valid_to = models.DateField('valid to',null=True,blank=True)
    def __unicode__(self):
            return self.a

class B(models.Model):
    #objects = models.Manager()
    objects = CurrentManager()
    a = models.ForeignKey(A)
    b = models.CharField(max_length=200)
    screenshot = models.ManyToManyField("Screenshot",through="ScreenshotToB")
    description = models.TextField(null=True,blank=True)
    valid_from = models.DateField('valid from')
    valid_to = models.DateField('valid to',null=True,blank=True)
    def __unicode__(self):
            return self.b

Edit-2

The accepted answer works for at least one relationship.
In case of a more nested data model, this method seems not to deliver the expected results:

models.py

class C(models.Model):
    objects = CurrentManager()
    b = models.ForeignKey(A)
    c = models.CharField(max_length=200)
    description = models.TextField(null=True,blank=True)
    valid_from = models.DateField('valid from')
    valid_to = models.DateField('valid to',null=True,blank=True)
    def __unicode__(self):
            return self.c

views.py

@login_required
def showA(request,a_id):
    a = A.objects.get(id=a_id)
    my_date = request.user.get_profile().my_date
    b_objects = a.b_set.current(my_date)
    c_objects = b_objects.c_set.current(my_date)
    t = loader.get_template('controltool2/showA.html')
    c = RequestContext(request,{'a':a,'b_objects':b_objects,'c_objects':c_objects,})
    return HttpResponse(t.render(c))

This returns the error: 'QuerySet' object has no attribute 'c_set'.

回答1:

I'd simplify it:

class CurrentManager(models.Manager):
    def current(self, my_date):
        return super(CurrentManager, self).get_query_set().filter(valid_from__lte=my_date) 

and then use it like this:

a = A.objects.get(id=a_id)
my_date = request.user.get_profile().my_date
b_objects = a.b_set.objects.current(my_date)

and then just pass a to the template as the filtered objects accessing them using this:

{% for b in b_objects %}

Hope this helps!

Edit (by requestor):

I had to adjust it as follows to get it working:

a = A.objects.get(id=a_id)
my_date = request.user.get_profile().my_date
b_objects = a.b_set.current(my_date)

This threw an error: "'RelatedManager' object has no attribute 'objects'"

a.b_set.objects.current(my_date)

来源：https://stackoverflow.com/questions/17778561/django-custom-manager-with-filter-parameter