rest_framework NOT NULL约束失败：tasks_tasks.assigner_id

Question

我提出一个应用程序，其中分配器可以将任务分配给受让人 当我运行的服务器，并尝试添加一个任务，我得到这个错误：

NOT NULL约束失败： tasks_tasks.assigner_id

这里是我的看法：

from rest_framework import viewsets, permissions 
from .models import Tasks 
from .serializers import TasksSerializer, UserSerializer 
from django.contrib.auth.models import User 


class UserViewSet(viewsets.ReadOnlyModelViewSet): 
    queryset = User.objects.all() 
    serializer_class = UserSerializer 


class TasksViewSet(viewsets.ModelViewSet): 
    queryset = Tasks.objects.all() 
    serializer_class = TasksSerializer 
    permission_classes = (permissions.IsAuthenticatedOrReadOnly,) 

    def prefrom_create(self, serializer): 
     serializer.save(self, assigner=self.request.user) 

这里是我的serializers.py

from rest_framework import serializers 
from .models import Tasks 
from django.contrib.auth.models import User 


class TasksSerializer(serializers.ModelSerializer): 
    assigner = serializers.ReadOnlyField(source='assigner.username') 

    class Meta: 
     model = Tasks 
     fields = ('id', 'url', 'title', 'description', 'assigner', 'assignee') 


class UserSerializer(serializers.ModelSerializer): 
    tasks = serializers.HyperlinkedIdentityField(many=True, view_name='tasks_details', read_only=True) 

    class Meta: 
     model = User 
     fields = ('id', 'url', 'username', 'tasks') 

，最后我的models.py：

from django.db import models 

class Tasks(models.Model): 
    created = models.DateTimeField(auto_now_add=True) 
    title = models.CharField(max_length=100) 
    description = models.TextField() 
    assigner = models.ForeignKey('auth.User', related_name='tasks', on_delete=models.CASCADE) 
    assignee = models.ForeignKey('auth.User', related_name='assigned', on_delete=models.CASCADE) 

    class Meta: 
     ordering = ('created',) 

Answer 1

你使assigner一个只读场源assigner.username - 这是你的问题。我想你可以解决这个问题通过定义两个字段而是一个READ_ONLY和一个WRITE_ONLY：

class TasksSerializer(serializers.ModelSerializer): 
assigner_name = serializers.ReadOnlyField(source='assigner.username') 
assigner = serializers.PrimaryKeyRelatedField(write_only=True, queryset=User.objects.all(), required=True) 
class Meta: 
    model = Tasks 
    fields = ('id', 'url', 'title', 'description', 'assigner', 'assignee', 'assigner_name') 

这段代码的作用是，当你的序列化是“写作”（反序列），它将接受出让方您将其传入存储方法的ID作为关键字参数assigner。然后，当它将任务序列化为json时，它会查找assigner.name，并将其返回到密钥assigner_name下，并错过assigner。

在视图中，你会再通过主键（而不是整个对象）到串行保存方法：

serializer.save(assigner=self.request.user.pk)