rest_framework NULL约束失败: tasks_tasks.assigner_id

Question

我正在制作一个应用程序，当我运行服务器并尝试添加一个任务时，转让人可以将任务分配给受让人，并尝试添加一个任务，我得到了以下错误：

NULL约束失败: tasks_tasks.assigner_id

以下是我的看法：

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

您已经将assigner设置为具有源assigner.username -this的只读字段，这是您的问题。我认为您可以通过定义两个字段(一个read_only和一个write_only)来解决这个问题：

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')

此代码的效果是，当您的序列化程序正在“写”(反序列化)时，它将接受您传递到保存方法中的转让人id作为关键字参数assigner。然后，当它将任务序列化到json时，它将查找assigner.name并在键assigner_name下返回它，而忽略了assigner。

在视图中，然后将主键(而不是整个对象)传递给序列化程序保存方法：

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