如何在 Django CreateView 中创建对象后添加指令？

Question

在我基于 class 的通用 CreateView 上，我想执行一条指令，从与当前创建的对象相关的另一个模型创建新对象。

Example: Collection is a model which is related to 3 differents Element objects. When I create a MyCollection object, which is related to a Collection and a User, 3 MyElement object must be created too and related to the newly created MyCollection object. One for each Element related to Collection.

# models.py

from django.contrib.auth.models import User
from django.db import models


class Collection(models.Model):
    # attributes and methods...


class Element(models.Model):
    collection = models.ForeignKey(Collection, # more arguments...)
    # more attributes and methods


class MyCollection(models.Model):
    user = models.ForeignKey(User, # more arguments...)
    collection = = models.ForeignKey(Collection, # more arguments...)
    # more attributes and methods

    def get_absolute_url(self):
        reverse(# some url with the object pk)


class MyElement(models.Model):
    element = models.ForeignKey(Element, # more arguments...)
    my_collection = models.ForeignKey(MyCollection, # more arguments...)
    # more attributes and methods

我正在使用 Django 的通用 CreateView，经过一些研究，我发现可以通过覆盖 get_success_url() 方法在 CreateView 中执行其他操作。

In my example, I did something similar:

# views.py

from django.views.generic import CreateView

from .utils import create_myelements_for_mycollection


class MyCollectionCreateView(CreateView):
    model = MyCollection
    # more attributes and methods...

    def get_success_url(self):
        create_myelements_for_mycollection(self.get_object())  # Here is where the bug occurs, works fine without this line

        return super().get_success_url()

# utils.py

from .models import Collection, Element, MyCollection, MyElement


def create_myelements_for_mycollection(my_collection):
    for element in my_collection.collection.elements_set.all():
        MyElement.objects.create(
            element=element,
            my_collection=my_collection,
        )

# urls.py

from django.urls import re_path

from . import views


urlpatterns = [
    re_path(
        r"^myelement/l/$",
        views.MyElementListView.as_view(),
    ),
    re_path(
        r"^myelement/r/(?P<pk>[0-9]+)/$",
        views.MyElementDetailView.as_view(),
    ),
    re_path(
        r"^myelement/c/(?P<element_pk>\d+)/$",
        views.MyElementCreateView.as_view(),
    ),

    re_path(
        r"^mycollection/l/$",
        views.MyCollectionListView.as_view(),
    ),
    re_path(
        r"^mycollection/r/(?P<pk>[0-9]+)/$",
        views.MyCollectionDetailView.as_view(),
    ),
    re_path(
        r"^mycollection/c/(?P<collection_pk>\d+)/$",
        views.MyCollectionCreateView.as_view(),
    ),
]

当我创建一个新的 MyCollection 对象时，所有 MyElements 都已在数据库中成功创建，但我收到此错误：

AttributeError: Generic detail view MyCollectionCreateView must be called with either an object pk or a slug in the URLconf.

我不明白为什么。

我的 CreateView url 没有任何 pk，因为当您创建一个新对象时，它还没有 pk。此外，MyCollection 有自己的 get_absolute_url。没有那个具体的指导，我工作正常。

谁能解释一下导致错误的原因，以及在对象创建后是否有更好的方法来执行这样的指令？

感谢您的帮助。

FYI:

Django 3.1
Pyhton 3.8

编辑

我尝试改用 post_save 信号（实际上写起来更干净），但我遇到了完全相同的错误。

# models.py

from django.db.models.signals import post_save
from django.dispatch import receiver

from .utils import create_myelements_for_mycollection


# ...models

@receiver(post_save, sender=MyCollection)
def create_myelements_for_mycollection(sender, instance, **kwargs):

    if instance is created:  # ? (Didn't look at how to write this condition in a signal yet)
        create_myelements_for_mycollection(my_collection)

AttributeError: Generic detail view MyCollectionCreateView must be called with either an object pk or a slug in the URLconf.

编辑 2

通过从 MyCollectionCreateView class 中删除 get_absolute_url() 覆盖，它确实有效。很好，但我仍然想知道问题出在哪里。如果这解决了问题，可能是我没看到的愚蠢行为。

# models.py

# ... previous code

class MyCollectionCreateView(CreateView):
    model = MyCollection
    # more attributes and methods...

    # Removing this solved the issue
    # def get_success_url(self):
    #     create_myelements_for_mycollection(self.get_object())
    #
    #     return super().get_success_url()

# more code ...

Answer 1

get_absolute_url() 在为模型创建新实例时使用，因为 django 必须知道在创建新 post 或创建新实例时去哪里。

来自错误

AttributeError: Generic detail view MyCollectionCreateView must be called with either an object pk or a slug in the URLconf.

它告诉您必须使用 object pk 或 slug 来调用它，因此您构建的 URL 就是问题所在。我不确定这种方法 create_myelements_for_mycollection() 是否满足这种需要。

理想情况下，您需要的是

def get_absolute_url(self):
    return f"/mycollection/{self.slug}/"

生成上述模式中的 URL，例如在锚标记中使用。

如何在 Django CreateView 中创建对象后添加指令？

How can I add an instruction after an object creation in Django CreateView?

python

django

create-view