禁止直接分配给多对多集的正面。改用emails_for_help.set（）

Question

我是Django的新手，但未找到有关此问题的任何参考。当我在Django模型（models.py）中使用多对多字段时，出现此错误。我猜问题是在views.pyform（forms.py）的view（）中分配m2m字段。

如何在视图中分配m2m字段？（Django version 2.0，python - 3.5）

models.py

class User(AbstractUser):
 username=models.CharField(max_length=20)
 email = models.EmailField(_('email address'), unique=True)

class Setupuser(models.Model):
 organization=models.CharField(max_length=200,blank=False,null=True)
 emails_for_help = models.ManyToManyField(User)

views.py

class Set_user(FormView):
 template_name="pkm_templates/set_up_user.html"
 form_class = Set_User_Form
 success_url = '/thanks/'

 def form_valid(self, form):
    org = form.cleaned_data.get('organization')
    emails = form.cleaned_data.get("emails_for_help")
    instance = Setupuser(organization=org,emails_for_help=emails)
    instance.save()
    return redirect("/")

表格

class Set_User_Form(ModelForm):
  emails_for_help = forms.ModelMultipleChoiceField(
    queryset=User.objects.all(),
    widget=forms.CheckboxSelectMultiple
  )

  class Meta:
    model = Setupuser
    fields = ["organization","emails_for_help"]

Answer 1

你需要获取User对象，然后将其添加到emails_for_help字段中。ManyToManyField创建实例时，不能向其添加对象。看一下doc。

class Set_user(FormView):
    template_name="pkm_templates/set_up_user.html"
    form_class = Set_User_Form
    success_url = '/thanks/'

    def form_valid(self, form):
        org = form.cleaned_data.get('organization')
        emails = form.cleaned_data.get("share_email_with")

        users = User.objects.filter(email__in=emails)
        instance = Setupuser.objects.create(organization=org)

        for user in users:
            instance.emails_for_help.add(user)

        return redirect("/")

编辑

这样做的另一种方法是使用.set()。

class Set_user(FormView):
    template_name="pkm_templates/set_up_user.html"
    form_class = Set_User_Form
    success_url = '/thanks/'

    def form_valid(self, form):
        org = form.cleaned_data.get('organization')
        emails = form.cleaned_data.get("share_email_with")

        users = User.objects.filter(email__in=emails)
        instance = Setupuser.objects.create(organization=org)

        instance.emails_for_help.set(users)

        return redirect("/")

或者，你可以简单地使用.add()添加任意数量的对象。

class Set_user(FormView):
    template_name="pkm_templates/set_up_user.html"
    form_class = Set_User_Form
    success_url = '/thanks/'

    def form_valid(self, form):
        org = form.cleaned_data.get('organization')
        emails = form.cleaned_data.get("share_email_with")

        users = User.objects.filter(email__in=emails)
        instance = Setupuser.objects.create(organization=org)

        instance.emails_for_help.add(*users)

        return redirect("/")