Call Django function with argument in html - django

Question

I am pretty new to django and try to call a django function in html to display how many objects of 'Akte' is in the respective 'Charge' object, but somehow I am missing the right way to do it.
models.py:
class Charge(models.Model):
STATI = (
('O','Offen'),
('G','Geschlossen'),
)
"Projektnr = models.CharField(max_length=30)"
Containernr = models.CharField(max_length=30)
Plombennr = models.CharField(max_length=30)
status = models.CharField(max_length=1, choices=STATI)
def __str__(self):
return self.Containernr
class Akte(models.Model):
Aktenbarcode = models.CharField(max_length=30)
"Eincheckdatum = models.datetime()"
user = models.CharField(max_length=30)
containerId = models.ForeignKey(Charge,on_delete=models.CASCADE)
kundennr = models.CharField(max_length=30)
Startdatum = models.DateField(auto_now_add=True)
def __str__(self):
return self.Aktenbarcode
and this is my views.py:
def tabelle(request):
assert isinstance(request, HttpRequest)
charge_list = Charge.objects.all()
return render(
request,
'app/tabelle.html',
{
'charge_list':charge_list,
}
)
def anzahl(containernr):
return {'anzahl': Akte.objects.filter(containerId__Containernr==containernr).count }
and here is the html code:
{% extends "app/ats.html" %}
{% block content %}
{% if not user.is_anonymous %}
<div style="margin-left:10%;color:white;"><a style="color:white"href="{% url 'home'%}">Home</a> ><a style="color:white"> Tabellenübersicht</a></div>
<div>
<table>
<tr>
<th>Containernummer</th>
<th>Status</th>
<th>Anzahl Akten</th>
<th>Plombennummer</th>
<th></th>
</tr>
{%for Charge in charge_list%}
<tr>
<td>{{Charge.Containernr}}</td>
<td>{{Charge.status}}</td>
<td>{% anzahl Charge.Containernr %}</td>
<td>{{Charge.Plombennr}}</td>
</tr>
{% endfor %}
</table>
</div>
{% endif %}
{% endblock %}
when I try it, I always get this error:
TemplateSyntaxError at /tabelle
Invalid block tag on line 19: 'anzahl(Charge.Containernr)', expected 'empty' or 'endfor'. Did you forget to register or load this tag?
what is the right way to solve this problem?

Answer 1

You can't call methods with arguments in the template. But you don't need to here; to get the count of Akte for that Charge you can do:
{{ Charge.akte_set.count }}
An even better - and much more efficient - approach is to get this data in the original query in your view, via annotation:
from django.db.models import Count
def tabelle(request):
charge_list = Charge.objects.all().annotate(akte_count=Count('akte'))
and now in your template you can do:
{{ Charge.akte_count }}