Django:如何通过多个模型级联更新

Question

我正在编写一个基于Django的应用程序来跟踪对象(Objekt(及其维护任务。对象可以链接到某个位置。

位置(0/1(---(n(对象(1(---(n(任务

Location、Objekt和Task都有一个状态字段，其值如下：

RED = "red"
YELLOW = "yellow"
GREEN = "green"
STATUS = [
(RED, "Overdue tasks"),
(YELLOW, "Pending tasks"),
(GREEN, "All good"),
]

我希望位置地图标记根据相关Objekt和最终任务的状态更改其颜色。

我试图遵循django的最佳实践，创建一个胖模型。

from django.db import models
from locationapp.models import Location
from taskapp.models import Task
from rules.contrib.models import RulesModel
class Objekt(RulesModel):
RED = "red"
YELLOW = "yellow"
GREEN = "green"
STATUS = [
(RED, "Overdue tasks"),
(YELLOW, "Pending tasks"),
(GREEN, "All good"),
]
name = models.CharField(max_length=200)
description = models.TextField(blank=True)
location = models.ForeignKey(
Location, on_delete=models.SET_NULL, null=True, blank=True
)
status = models.CharField(max_length=6, choices=STATUS, default=GREEN)
def set_status(self):
if Task.objects.filter(objekt=self.id).filter(status=Task.RED).exists():
self.status = Objekt.RED
elif Task.objects.filter(objekt=self.id).filter(status=Task.YELLOW).exists():
self.status = Objekt.YELLOW
else:
self.status = Objekt.GREEN

但不知怎么的，我不确定我在这里的概念。。。任务的更新如何触发相关对象的更新。如果需要的话，Objekt将如何进一步触发位置更新？

Answer 1

一个潜在的解决方案是使用信号。我已经实现了如下，目前没有芹菜：

# objektapp/apps.py
from django.apps import AppConfig

class ObjektappConfig(AppConfig):
default_auto_field = 'django.db.models.BigAutoField'
name = 'objektapp'
def ready(self):
import objektapp.signals

# objektapp/signals.py
from django.db.models.signals import post_save
from django.dispatch import receiver
from django.db import transaction
from taskapp.models import Task
from objektapp.models import Objekt
@receiver(post_save, sender=Task)
def set_status(sender, instance, created, **kwargs):
# TODO: Use celery for async operation: https://docs.djangoproject.com/en/3.2/topics/db/transactions/
transaction.on_commit(lambda: objekt_update_status(instance))
def objekt_update_status(task_instance):
objekt = Objekt.objects.get(id=task_instance.objekt.id)
new_objekt_status = Objekt.GREEN
if Task.objects.filter(objekt=task_instance.objekt.id, status=Task.RED).exists():
new_objekt_status = Objekt.RED
elif Task.objects.filter(objekt=task_instance.objekt.id, status=Task.YELLOW).exists():
new_objekt_status = Objekt.YELLOW
if objekt.status != new_objekt_status:
objekt.status = new_objekt_status
objekt.save()

我在Location模型上做过类似的设置，它也会对Objekt的postrongave信号做出反应。我不确定这是否是将objekt_update_status((函数存储在signals.py文件中的最佳位置，但试图将其放入models.py中时却出现了循环导入错误。