Django rest PUT 请求序列化程序无法使用外键更新模型

Question

我有两个模型，如下所示：

class Task(models.Model):
user = models.ForeignKey(User, blank=True)
what_task = models.CharField(max_length=100, )
#This helps to print in admin interface
def __str__(self):
return u"%s" % (self.what_task)

class Step(models.Model):
task = models.ForeignKey(Task, related_name='steps', on_delete=models.CASCADE, )
what_step = models.CharField(max_length=50, blank=True, )
#This helps to print in admin interface
def __str__(self):
return u"%s" % (self.what_step)

我写了序列化程序：

class StepSerializer(serializers.ModelSerializer):
class Meta:
model = Step
exclude = ('task',)
class TaskSerializer(serializers.ModelSerializer):
steps = StepSerializer(many=True)
class Meta:
model = Task
fields = '__all__'

def create(self, validated_data):
steps_data = validated_data.pop('steps')
task = Task.objects.create(**validated_data)
for step_data in steps_data:
Step.objects.create(task=task, **step_data)
return task 
def update(self, instance, validated_data):
steps_data = validated_data.pop('steps')
instance.what_task = validated_data.get('what_task', instance.what_task)
instance.how_often = validated_data.get('how_often', instance.how_often)
instance.how_important = validated_data.get('how_important', instance.how_important)
instance.why_perform = validated_data.get('why_perform', instance.why_perform)
instance.why_important = validated_data.get('why_important', instance.why_important)
instance.possible_improvement = validated_data.get('possible_improvement', instance.possible_improvement)
instance.existing_solutions = validated_data.get('existing_solutions', instance.existing_solutions)
instance.how_important_improvement = validated_data.get('how_important_improvement', instance.how_important_improvement)
instance.advantages_of_improvement = validated_data.get('advantages_of_improvement', instance.advantages_of_improvement)
instance.save()
for step_data in steps_data:
Step.objects.update(task=task, **step_data)
return instance 

我的观点：

@api_view(['GET', 'POST'])
def task_list(request):
"""
List all tasks, or create a new task.
"""
if request.method == 'GET':
print(request.user)
tasks = Task.objects.filter(user=request.user.id)
serializer = TaskSerializer(tasks, many=True)
return Response(serializer.data)
elif request.method == 'POST':
serializer = TaskSerializer(data=request.data)
print(request.data)
if serializer.is_valid():
serializer.save(user=request.user)
return Response(serializer.data, status=status.HTTP_201_CREATED)
else:
return Response(
serializer.errors, status=status.HTTP_400_BAD_REQUEST)

@api_view(['GET', 'PUT', 'DELETE'])
def task_detail(request, id):
"""
Get, udpate, or delete a specific task
"""
try:
task = Task.objects.get(id=id)
except Task.DoesNotExist:
return Response(status=status.HTTP_404_NOT_FOUND)
if request.method == 'GET':
serializer = TaskSerializer(task)
return Response(serializer.data)
elif request.method == 'PUT':
serializer = TaskSerializer(task, data=request.data)
if serializer.is_valid():
serializer.save(user=request.user)
return Response(serializer.data)
else:
return Response(
serializer.errors, status=status.HTTP_400_BAD_REQUEST)
elif request.method == 'DELETE':
task.delete()
return Response(status=status.HTTP_204_NO_CONTENT)

我的GET和POST请求工作正常(视图中的第一个函数(，我的任务和相关步骤是在单个请求中创建的，但是PUT请求是错误的，我不确定我是否正确更新了步骤;如果我从 for 循环serializer注释掉，任务更新成功。

我应该修改什么以及如何修改，以便可以使用相关步骤更新特定任务？

Answer 1

在 for 循环中，您更新每个现有任务(在update中，您可以设置新值(：

Step.objects.update(task=task, **step_data)

相反，在循环之前，您应该删除该任务的所有步骤并创建新步骤：

...
Step.objects.filter(task=instance).delete()
for step_data in steps_data:
Step.objects.create(task=instance, **step_data)
...

更有效的方法是查找validated_data中不存在的所有步骤(基于 id(并删除它们，使用 id 更新步骤，创建没有 id 的步骤。