Not working (well) with @property fields

[Former user]

This is something that I have found using properties to show a combinations of 2 fields, can't use str or unicode so I have create a property field on my Django model some like:

class Area(models.Model):
    name = models.CharField(max_length=100)
    short_name = models.CharField(max_length=10, unique=True)
    # Other fields

    def __str__(self):
        return '%s (%s)' % (self.name, self.short_name)

    @property
    def area(self):
        return '%s (%s)' % (self.name, self.short_name)

However, when I declare the BaseDatatableView, with:

    columns = ['area', 'other_field']

The JSON response looks ok, but, on view throws a "7. Warning: Ajax error", on terminal says:

django.core.exceptions.FieldError: Cannot resolve keyword 'area' into field. Choices are: name, short_name, [...]

If I add another field on the first place, it shows everything normal, but, repeats the first element at least twice.

[Alex Franco]

I created this issue, without login in... sorry

[Maciej Wisniowski]

There is no full traceback included so it is a bit hard to guess the exact location of this exception. I suppose that this is caused by order_columns (its definition is not shown in your samples). If you're using your property name within order_columns then it will fail as there is no 'area' field in the database.

Anyway I'd suggest not using property but aggregate on your queryset, eg:

from django.db import models
from django.db.models import CharField, Value as V
from django.db.models.functions import Concat

qs = Area.objects.annotate(area=Concat(F('name), V(' ('), F('short_name'), V(')'), output_field=models.TextField())

This way you'll have 'area' field that is filterable and orderable. See: https://docs.djangoproject.com/en/2.1/ref/models/database-functions/#concat