如何在 Django 中保存多对多关系

Question

How to create an object for a Django model with a many to many field?

从上面的问题我知道我们只能在以后保存多对多字段。

models.py

class Store(models.Model):
   name = models.CharField(max_length=100)

class Foo(models.Model):
   file = models.FileField(upload_to='')
   store = models.ManyToManyField(Store, null=True, blank=True)

views.py

new_track.file = request.FILES['file']
new_track.save()

文件上传工作正常，然后我修改我的代码以添加商店，然后我就在这里......

现在我确定 db return id 在这里。然后我尝试了下面的代码，但这只是给了我错误

    x = new_track.id
    new = Foo.objects.filter(id=x)
    new.store.id = request.POST['store']
    new.save()

好的，这里的错误是'QuerySet' object has no attribute 'store'

我还尝试了add，现在也可以使用。 所以问题是如何保存（）

Answer 1

截至 2020 年，这是我将 ManyToMany 字段保存到给定对象的方法。

简答

class HostingRequestView(View):
    def post(self, request, *args, **kwargs):
        form = VideoGameForm(request.POST)
        if form.is_valid():
            obj = form.save(commit=False)
            obj.updated_by = request.user
            obj.save()

            selected_categories = form.cleaned_data.get('category') #returns list of all selected categories e.g. ['Sports','Adventure']
            #Now saving the ManyToManyField, can only work after saving the form
            for title in selected_categories:
                category_obj = Category.objects.get(title=title) #get object by title i.e I declared unique for title under Category model
                obj.category.add(category_obj) #now add each category object to the saved form object
            return redirect('confirmation', id=obj.pk)

完整答案

models.py

class Category(models.Model):
    title = models.CharField(max_length=100, null=True, unique=True)

class VideoGame(models.Model):
    game_id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=50, blank=False, null=False)
    updated_by = models.ForeignKey(settings.AUTH_USER_MODEL, blank=False, on_delete=models.CASCADE)
    category = models.ManyToManyField(Category) #ManyToMany Category field
    date_added = models.DateTimeField(auto_now_add=True, verbose_name="date added")

forms.py 模型表单

class VideoGameForm(forms.ModelForm):
    CATEGORIES = (
        ('Detective', 'Detective'),
        ('Sports', 'Sports'),
        ('Action', 'Action'),
        ('Adventure', 'Adventure'),
    )

    category = forms.MultipleChoiceField(choices=CATEGORIES, widget=forms.SelectMultiple())

    class Meta:
        model = VideoGame
        fields = ['name', 'category', 'date_added']

post 上的views.py

class HostingRequestView(View):
    def post(self, request, *args, **kwargs):
        form = VideoGameForm(request.POST)
        if form.is_valid():
            obj = form.save(commit=False)
            obj.updated_by = request.user
            obj.save()

            selected_categories = form.cleaned_data.get('category') #returns list of all selected categories e.g. ['Sports','Adventure']
            #Now saving the ManyToManyField, can only work after saving the form
            for title in selected_categories:
                category_obj = Category.objects.get(title=title) #get object by title i.e I declared unique for title under Category model
                obj.category.add(category_obj) #now add each category object to the saved form object
            return redirect('confirmation', id=obj.pk)

重定向的 URL 路径

urlpatterns = [
    path('confirmation/<int:id>/', Confirmation.as_view(), name='confirmation'),
]

我希望这会有所帮助。问候

Answer 2

保存具有多对多关系的对象的正确方法是：

...
new_track.file = request.FILES['file']
new_track.save()

new_store = Store.objects.get(id=int(request.POST['store']))
new_track.store.add(new_store)

Answer 3

为什么这么混乱..你在那里得到了 id，像这样打电话给商店

new_track.save()
new_track.store.add(request.POST['store'])

Answer 4

也许：

1. 将 Foo 更改为 Tracks
2. Tracks.objects.filter(id=x) 到 Tracks.objects.get(id=x)

告诉我进展如何

Answer 5

new.stores.all()

返回链接到该对象的所有商店。