Cross queries in django - django

Question

I have two models as below
class Watched(Stamping):
user = models.ForeignKey("User", null=True, blank=True, on_delete=models.CASCADE,
default=None)
count = models.PositiveIntegerField()
class Link(Stamping):
...
user = models.ForeignKey(User, on_delete=models.CASCADE, default=None)
url = models.CharField(max_length=256, default=None)
watched = models.ForeignKey(Watched, null=True, blank=True, on_delete=models.CASCADE, default=None)
...
My forms.py
class SimpleLink(forms.Form):
url = forms.URLField(max_length=256)
A user can create a Link object and when some conditions are met, the object will be added to Watched. The Watched model contains objects created by different users.
Now I want to filter the Watched class and grab only the objects created by the requesting user in the Link model but I don't know how I can achieve that. Any help will be appreciated.
A sample of what I want to achieve is...
Watched.objects.filter(Link.objects.filter(user=request.user). I know my sample is crazy. But from the outside query, I want to grab the Link objects created by user making the request

Answer 1

You need to limit the queryset in your ModelForm. A ModelForm will thus look like:
from django import forms
class LinkForm(forms.ModelForm):
def __init__(self, *args, user=None, **kwargs):
super().__init__(*args, **kwargs)
if user is not None:
self.fields['watched'].queryset = Watched.objects.filter(
link__user=user
)
class Meta:
model = Link
fields = ['url', 'watched']
In our view, we can then set the user object:
from django.contrib.auth.decorators import login_required
from django.shortcuts import redirect, render
#login_required
def some_view(request):
if request.method == 'POST':
form = LinkForm(request.POST, user=request.user)
if form.is_valid():
form.instance.user = request.user
form.save()
return redirect('name-of-some-form')
else:
form = LinkForm(user=request.user)
return render(request, 'some-template.html', {'form': form})
For a class-based view, we can override the .get_form_kwargs(…) method [Djangod-doc]:
from django.contrib.auth.mixins import LoginRequiredMixin
class SomeView(LoginRequiredMixin, CreateView):
form_class = LinkForm
def get_form_kwargs(self):
kwargs = super().get_form_kwargs()
kwargs['user'] = self.request.user
return kwargs
def form_valid(self, form):
form.instance.user = self.request.user
return super().form_valid(form)