如何删除ManyToMany字段的实例？

Question

我有两个型号：

class Organisation(models.Model):
    user        = models.OneToOneField(settings.AUTH_USER_MODEL,related_name='organisation_user',on_delete=models.CASCADE)
    name        = models.CharField(max_length=100,blank=True)
    location    = models.CharField(max_length=100,blank=True)
    qualification_status = (
        ('Pending for verification','Pending for verification'),
        ('Verified','Verified'),
        )
    qualification   = models.CharField(max_length=100,choices=qualification_status,default='Pending for verification',blank=True)
    members         = models.ManyToManyField(settings.AUTH_USER_MODEL,related_name='organisation_members',blank=True)

class Organisation_member(models.Model):
    user            = models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE,null=True,blank=True)
    organisation    = models.ForeignKey(Organisation,on_delete=models.CASCADE,related_name='organisation_staff')
    member_name     = models.ForeignKey(settings.AUTH_USER_MODEL,related_name='organisation_staff_member',on_delete=models.CASCADE,null=True,blank=True)
    is_admin        = models.BooleanField(default=False)

我有这个信号用于创建Organisation_member模型：

@receiver(post_save, sender=Organisation)
def organisation_admin(sender, instance, created, **kwargs):
    for member in instance.members.all():
        if Organisation_member.objects.filter(user=instance.user,organisation=Organisation.objects.filter(user=instance.user,name=instance.name).first(),member_name=member).exists():
            pass
        else:
            Organisation_member.objects.update_or_create(User=instance.User,organisation=Organisation.objects.filter(user=instance.user,name=instance.name).first(),member_name=member,is_admin=False)

该信号表示当我在manytomany字段中添加成员时，它将自动创建所选成员的Organisation_member对象。

信号完全正常。

我的问题是相反的，即当我尝试删除Organisation_member的对象时，它也应该从父模型的manytomany关系中删除该成员。

我试过这个：

@login_required()
def delete_members(request, pk):
    user_organisation = get_object_or_404(Organisation, user=request.user)
    member_to_delete = Organisation_member.objects.filter(pk=pk)
    if member_to_delete.exists():
        member_to_delete[0].delete()
        for member in user_organisation.members.all():
            user_organisation.members.remove(member=member_to_delete[0])
    return redirect(reverse('userprofile:organisation_member_list'))

但它不会从父模型中删除成员..

知道解决方案的任何人都可以帮忙。

谢谢

Answer 1

尝试这样的事情：

@login_required()
def delete_members(request, pk):
    user_organisation = get_object_or_404(Organisation, user=request.user)
    member_to_delete = get_object_or_404(Organisation_member, pk=pk)
    user_organisation.members.remove(member_to_delete.member_name)
    member_to_delete.delete()
    return redirect(reverse('userprofile:organisation_member_list'))

Refer Django offical doc

Answer 2

使用这种关系的标准方法是将Organisation_member指定为through中members的Organisation模型。然后数据库会在没有任何信号的情况下为您处理。

class Organisation(models.Model):
    members = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        through='Organisation_member')

唯一的问题是你目前在User中有两个Organisation_member的引用：member_name和user。为什么？你可能只需要一个，应该删除另一个。如果在Organisation_member中有两个不同用户的原因，则需要指定用于关系的字段：

    members = models.ManyToManyField(
        settings.AUTH_USER_MODEL,
        through='Organisation_member',
        through_fields=('organisation', 'member_name'))

就是这样，无论何时向Organisation_member添加或删除用户，都会自动添加和删除memberss。