在 django 中创建一个嵌套类并运行一个帮助程序方法

Question

我有以下用户模型，

class User(AbstractBaseUser, PermissionsMixin, Base):
username = models.CharField(max_length=255, null=False)
email = models.CharField(max_length=255, null=False, unique=True)
user_type = models.CharField(max_length=255, null=False)
is_staff = models.BooleanField(default=False)
is_superuser = models.BooleanField(default=False)
is_active = models.BooleanField(default=False)

这是我的会议模型

class Meeting(Base):
meeting_code = models.CharField(max_length=255)
owner = models.ForeignKey(User, related_name='meetings', on_delete=models.CASCADE, null=True, blank=True)
members = models.ManyToManyField(User, related_name='meeting_set', null=True, blank=True)
start_time = models.DateTimeField(auto_now_add=True)
end_time = models.DateTimeField(null=True)

创建会议时，我想运行此帮助程序函数来生成会议代码

def generate_meetingid():
return ''.join(random.choices(string.ascii_uppercase, k=16))

这是我的会议序列化程序，

class MeetingSerializer(serializers.ModelSerializer):
owner = UserSerializer(required=True)
class Meta:
model = Meeting
fields = ['id', 'meeting_code', 'owner', 'members', 'start_time', 'end_time', ]

我的问题是，如何编写将创建用户添加为所有者并运行帮助程序方法来创建会议代码的会议视图集。 从本质上讲，我正在尝试完成这个视图，

class MeetingViewSet(viewsets.ModelViewSet):
queryset = Meeting.objects.all()
serializer_class = MeetingSerializer
def perform_create(self, serializer):
serializer.save()

Answer 1

最简单的方法是覆盖save方法，而我通常更喜欢使用pre_save信号。该逻辑类似于为模型实例生成唯一slug，在保存对象之前会自动调用帮助程序函数。在序列化程序中，只需将meeting_code标记为read_only，以便在反序列化期间创建或更新实例时不使用meeting_code

# override save method
class Meeting(models.Model):
...
def save(self, *args, **kwargs):
# avoid meeting_code IntegrityError
# self._state.adding == True means item was not added in the database yet
if self._state.adding and not self.meeting_code:
self.meeting_code = generate_meetingid()
while Meeting.objects.filter(meeting_code=self.meeting_code).exists():
self.meeting_code = generate_meetingid()
super().save(*args, **kwargs)

# pre_save signal
@receiver(pre_save, sender=Meeting)
def generate_meeting_code(sender, **kwargs):
if kwargs.get('created', False):
# on meeting create
meeting=kwargs.get('instance')
meeting.meeting_code = generate_meetingid()
while Meeting.objects.filter(meeting_code=self.meeting_code).exists():
meeting.meeting_code = generate_meetingid()

序列化程序

class MeetingSerializer(serializers.ModelSerializer):
owner = UserSerializer(required=True)
class Meta:
model = Meeting
fields = ['id', 'meeting_code', 'owner', 'members', 'start_time', 'end_time', ]
read_only_fields = ['meeting_code']

视图

class MeetingViewSet(viewsets.ModelViewSet):
queryset = Meeting.objects.all()
serializer_class = MeetingSerializer
def perform_create(self, serializer):
# pass owner to the serializer
serializer.save(owner=self.request.user)