在一个模型内分配Django模型字段以指向其他相关模型中的一种

Question

I am designing an inspection app in Django for a service company and have an esoteric question about my models. This is the scenario I'm struggling with:

Site(models.Model):
    name = CharField()

Generator(models.Model):
    number = CharField()
    site = ForeignKey(Site)

Pump(models.Model):
    number = CharField()
    site = ForeignKey(Site)

Jobs(models.Model):
    asset = ?
    site = ForeignKey(Site)

What I would like to do is assign either a Generator OR a Pump object to the asset field in Jobs. Rather than just generating a list of both generator and pump numbers I would like the field to point to the actual model itself, that way I can backwards reference each job without scanning both tables.

Any ideas? Would it help to have an asset property in the job model? I am overthinking this?

Using Django 1.11.1 and Python 3.6

Answer 1

You can use a generic foreign key as seen in the documentation

Since this is a one-line answer. To expand upon that:

from django.db import models
from django.contrib.contenttypes.fields import GenericRelation
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType

class Asset(models.Model):

    content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
    object_id = models.PositiveIntegerField()
    content_object = GenericForeignKey('content_type', 'object_id')
    ...

class Job(models.Model):

    assets = GenericRelation(Asset)
    ...