One way I can think of is to add a property
<https://docs.python.org/3/library/functions.html#property> to your model.
I believe something like this should work:
```
## in your model class:
mother_alive = models.IntegerField(choices=YES_NO_CHOICES, blank=True,
null=True, default=1)
father_alive = models.IntegerField(choices=YES_NO_CHOICES, blank=True,
null=True, default=1)
@property
def is_orphan(self):
return self.mother_alive == 0 and self.father_alive == 0 # not
sure what the "no" value is, you have to set it appropriately
```
You'll then be able to access it as an attribute of the model:
```
Child.objects.get(id=1).is_orphan
# True or False
```
This value will not be stored in the database, though, and you won't be
able to filter children by the `is_orphan` column, because there'll be no
such column.
Another approach would be to use annotations
<https://docs.djangoproject.com/en/2.2/ref/models/querysets/#django.db.models.query.QuerySet.annotate>.
With annotations, you can do aggregations, just like with any other model
field.
On Monday, 21 October 2019 20:05:04 UTC+2, Eileen Bauer wrote:
>
> Hi,
> i have the following items in my model:
> mother_alive = models.IntegerField(choices=YES_NO_CHOICES, blank=True,
> null=True, default=1)
> father_alive = models.IntegerField(choices=YES_NO_CHOICES, blank=True,
> null=True, default=1)
>
> and I'd like to set up a generated field for them so I'd be able to detect
> whether the child is an orphan or not. In MySQL i believe it'd look like
> this:
> orphan varchar(101) GENERATED ALWAYS AS (mother_alive+father_alive)
> VIRTUAL,
>
> I don't know how to change my model to do that...
>
> Any help?
>
> -Eileen
>
>
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