如何修复模型的 Django 实例

Question

错误消息AttributeError: 'NoneType' 对象没有属性 'add'

我正在尝试创建模型的实例。 卡片模型假设是患者模型的一个实例，患者模型与用户模型有外键关系。 就像一个病人在医院里有一张卡。

我的错误来自 perform_create 方法

视图.py

class PatientCardListAPIView(ListCreateAPIView):
    serializer_class = PatientsCardSerializer
    queryset = Card.objects.all()
    permission_classes = (permissions.IsAuthenticated, IsOwner,  ) 
    def perform_create(self, serializer):
        serializer.save()
        serializer.instance.owner.add(self.request.user)

模型.py

from django.db import models
from authentication.models import User
# Create your models here.

class Patient(models.Model):
    name = models.CharField(max_length=255, null=True)
    country = models.CharField(max_length=255, null=True)
    state = models.CharField(max_length=255, null=True)
    phone = models.CharField(max_length=255, null=True)
    email = models.CharField(max_length=255, null=True)
    owner = models.ForeignKey(to=User, null=True, on_delete=models.CASCADE)
    def __str__(self):
        return self.name
        


class Card(models.Model):    
    name = models.CharField(max_length=255, null=True)
    card_number = models.CharField(max_length=255, null=True)    
    owner = models.OneToOneField(Patient, null=True, blank=True, on_delete=models.CASCADE)
    
    def __str__(self):
        return self.name
        
        

Answer 1

它应该是

class PatientCardListAPIView(ListCreateAPIView):
    serializer_class = PatientsCardSerializer
    queryset = Card.objects.all()
    permission_classes = (permissions.IsAuthenticated, IsOwner,)

    def perform_create(self, serializer): serializer.save(owner = self.request.user) 

Answer 2

这应该是：

def perform_create(self, serializer):
    model_instance = serializer.save(owner=self.request.user)

或者

def perform_create(self, serializer):
    model_instance = serializer.save()
    model_instance.owner = self.request.user

已编辑........... 仔细查看您的模型表明您需要重新定义模型。 正如您所定义的，Patient 类下的owner字段表明您可以拥有一个 User 可以是多个 Patient...（查询： patient=Patient.objects.get(owner=self.request.user)可能会返回不止一个实例。）。 建议的型号应该是：

class Patient(models.Model):
    name = models.CharField(max_length=255, null=True)
    country = models.CharField(max_length=255, null=True)
    state = models.CharField(max_length=255, null=True)
    phone = models.CharField(max_length=255, null=True)
    email = models.CharField(max_length=255, null=True)
    **owner = models.OneToOneField(User, null=True)**
    def __str__(self):
        return self.name

class Card(models.Model):    
    name = models.CharField(max_length=255, null=True)
    card_number = models.CharField(max_length=255, null=True)    
    owner = models.OneToOneField(Patient, null=True, blank=True, on_delete=models.CASCADE)

    def __str__(self):
        return self.name

然后你可以有你的看法：

class PatientCardListAPIView(ListCreateAPIView):
    serializer_class = PatientsCardSerializer
    queryset = Card.objects.all()
    permission_classes = (permissions.IsAuthenticated, IsOwner,  ) 
    
    def perform_create(self, serializer):
        card_instance = serializer.save()
        patient = Patient.objects.get(owner=self.request.user)
        card_instance.owner = patient

Answer 3

感谢我几乎用编程的，因为这个问题在过去的24小时气馁，而是这个社会帮助了我，即使他们没有给我所需要的答案，他们把我带进发现自己的答案，和我说谢谢你的StackOverflow社区...

解决了我终于发现我做错了什么。 一张卡不仅属于患者，也属于医院，因此卡需要与医院和患者都有关系。

模型.py

 class Patient(models.Model):
        name = models.CharField(max_length=255, null=True)
        country = models.CharField(max_length=255, null=True)
        state = models.CharField(max_length=255, null=True)
        phone = models.CharField(max_length=255, null=True)
        email = models.CharField(max_length=255, null=True)
        owner = models.ForeignKey(to=User, null=True, on_delete=models.CASCADE)
        def __str__(self):
            return self.name      
    
    class Card(models.Model):    
        name = models.CharField(max_length=255, null=True)
        card_number = models.CharField(max_length=255, null=True)    
        owner = models.OneToOneField(Patient, null=True, blank=True, on_delete=models.CASCADE)
        hospital = models.ForeignKey(User, null=True, blank=True, on_delete=models.CASCADE)        
        def __str__(self):
            return self.name

视图.py

class PatientCardListAPIView(ListCreateAPIView):
    serializer_class = PatientsCardSerializer
    queryset = Card.objects.all()
    permission_classes = (permissions.IsAuthenticated, IsOwner,  )         
    def perform_create(self, serializer):
        return serializer.save(hospital=self.request.user)
    def get_queryset(self):
        return self.queryset.filter(hospital=self.request.user)

class PatientCardDetailAPIView(RetrieveUpdateDestroyAPIView):
    serializer_class = PatientsCardSerializer
    permission_classes = (permissions.IsAuthenticated, IsOwner,)
    queryset = Card.objects.all()
    lookup_field = "id"
    def get_queryset(self):
        return self.queryset.filter(hospital=self.request.user)