在Django/REST中保存多对多模型? [英] Save a many-to-many model in Django/REST?
问题描述
我正在为我的Django应用程序编写REST API,并且无法获取POST请求以在一种模型上工作. 这是有问题的模型:
I'm writing a REST API for my Django app, and can't get POST requests to work on one model. Here's the model in question:
class ProjectNode(models.Model):
name = models.CharField(max_length=60)
place = models.CharField(max_length=150)
time_spent = models.BigIntegerField()
parent_project = models.ForeignKey(Project, related_name='tasks')
workers = models.ManyToManyField(User, related_name='tasks_can_do')
def __str__(self):
return self.name
User
模型目前仅保存一个name
字段.
这是我的ProjectNode
的序列化器:
The User
model just holds a name
field at the moment.
Here's my serializer for ProjectNode
:
class ProjectNodeSerializer(serializers.ModelSerializer):
class Meta:
model = ProjectNode
fields = ('id', 'name', 'place', 'time_spent', 'workers',)
这是API视图(来自views.py
):
And here's the API view (from views.py
):
class WebProjectNodeListView(generics.ListCreateAPIView):
queryset = ProjectNode.objects.all()
serializer_class = ProjectNodeSerializer
def pre_save(self, obj):
obj.parent_project = Project.objects.get(pk=self.request.DATA['parent_project'])
for worker_pk in self.request.DATA['workers']:
obj.workers.add(User.objects.get(pk=worker_pk))
obj.final_worker = User.objects.get(pk=self.request.DATA['final_workers'])
昨天我起初尝试了一个更简单的版本,该版本仅具有Project
ForeignKey关系,而且似乎可以正常工作,所以我认为使用add
也可以工作,但是在测试API时出现错误使用httpie
(我已经添加了一些用户和项目,并确保我正确获得了他们的ID).
这是请求:
I tried a simpler version yesterday at first, which only had the Project
ForeignKey relationship, and it seemed to work, so I thought that using add
would work too, but I get an error when testing out the API with httpie
(I already added some users and projects, and am sure I get their id's correctly).
Here's the request:
http POST :8000/api/tasks/ name="newtask" place="home" time_spent:=50 parent_project:=1 workers:=[1]
我收到此错误:
"<ProjectNode: newtask>" needs to have a value for field "projectnode" before this many-to-many relationship can be used.
回溯也指向以下代码行:
And the traceback also points to this line of code:
obj.workers.add(User.objects.get(id=worker_pk))
现在,我感觉这是因为我试图在数据库中创建ProjectNode
对象之前更新User
对象上的关系,但是我不确定如何解决此问题?
Now, I get the feeling that this is because I'm trying to update the relationship on the User
object before a ProjectNode
object is created in the database, but I'm not sure how to resolve this?
推荐答案
DRF无法创建嵌套序列化程序对象或多对多"字段的模型.
因此有必要在创建ProjectNode之前重写Serializer的创建方法并创建/获取M2M模型.
尝试在序列化程序中覆盖create(self, validated_data)
,然后在此方法中使用数据.
DRF doesn't works create models which are nested serializers objects or Many to Many fields.
So is necessary to override Serializer create method and create/get M2M models before create ProjectNode.
Try to override create(self, validated_data)
in your serializer and work with your data inside this method..
示例:
我的模型Project与ProjectImages具有M2M关系.在ProjectSerializer中,我像这样重写了create方法.
My model Project has M2M relation with ProjectImages. In ProjectSerializer I override create method like this.
def create(self, validated_data):
try:
# Remove nested and M2m relationships from validated_data
images = validated_data.pop('projectimage_set') if 'projectimage_set' in validated_data else []
# Create project model
instance = Project(**validated_data)
if status:
instance.set_status(status)
project = instance.save()
# Create relations
for image in images:
ProjectImage.objects.create(project=project, **image)
except exceptions.ValidationError as e:
errors_messages = e.error_dict if hasattr(e, 'error_dict') else e.error_list
raise serializers.ValidationError(errors_messages)
return project
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