Django-Filter over Managers - django

Question

I've been stuck in this for several weeks now and I believe the answer is super simple but somehow I can't find it anywhere online. Which makes me think I'm going about it totally wrong.
All I want to do is be able to filter my stats such as the get_largest_winning_trade function based on the django-filter package. Where am I going wrong? As a side note get_largest_winning_trade is showing the largest winning trade in the Trade Model but it is not being filtered for my criteria. Such as "user".
managers.py
from django.db import models
class TradeQuerySet(models.QuerySet):
def get_users_trades(self, username):
return self.filter(user__username=username)
class TradeManager(models.Manager):
def get_queryset(self):
return TradeQuerySet(self.model, using=self._db)
def get_users_trades(self, username):
return self.get_queryset().get_users_trades(username)
def get_largest_winning_trade(self):
return max([t.profit_loss_value_fees for t in self.all()])
views.py
class StatsView1(LoginRequiredMixin, ListView):
model = Trade
template_name = 'dashboard/stats1.html'
def get_context_data(self, **kwargs):
filter = StatsFilter1(self.request.GET, queryset=self.get_queryset())
context = super().get_context_data(**kwargs)
context['filter'] = filter
context['get_largest_winning_trade'] = Trade.objects.get_largest_winning_trade
return context
stats.html (testing)
filter.qs.get_largest_winning_trade: {{ filter.qs.get_largest_winning_trade }} <br>
Trade.get_largest_winning_trade: {{ Trade.get_largest_winning_trade }} <br>
trade.get_largest_winning_trade: {{ trade.get_largest_winning_trade }} <br>
get_largest_winning_trade: {{ get_largest_winning_trade }} <br> # works but not with filter
Additional Requested Information
Shared the class, it's quite long so I tried to reduce it to what is most helpful. Please let me know if there's anything else.
models.py
class Trade(models.Model):
class Meta:
verbose_name = "Trade"
verbose_name_plural = "Trades"
...
user = models.ForeignKey(User, on_delete=models.CASCADE, blank=True)
status = models.CharField(max_length=2, choices=STATUS_CHOICES, default='cl')
type = models.CharField(max_length=5, choices=TYPE_CHOICES, default=LONG)
broker = models.ForeignKey(Broker, on_delete=models.CASCADE, blank=True, null=True)
asset = models.ForeignKey(Asset, default=DEFAULT_ASSET_ID, on_delete=models.CASCADE, null=True)
#AUTOMATED FIELDS
profit_loss_value_fees = models.FloatField(null=True)
objects = TradeManager()
...
def save(self):
...
self.profit_loss_value_fees = self.get_profit_loss_value_fees()
return super(Trade, self).save()
...

Answer 1

Probably you can do something like this using qs property:
def get_context_data(self, **kwargs):
filter = StatsFilter1(self.request.GET, queryset=self.get_queryset())
context = super().get_context_data(**kwargs)
context['filter'] = filter
context['get_largest_winning_trade'] = filter.qs.get_largest_winning_trade
return context
Update
I think rather than doing it manager, you can do the calculation here with aggregation. Like this:
from django.db.models import Max
...
context['get_largest_winning_trade'] = filter.qs.aggregate(max_value=Max('profit_loss_value_fees'))['max_value']
Reason for using aggregation is to reduce DB hits, because your manager method will hit database multiple times during loop iteration.