Django REST: How to PUT Data in Nested ModelSerializer (Update)

Question

Now I can POST a new data to my django app by json ,but can't update the data or delete it. I try to override the update method in the serializer.py, but it still doesn't work. The data keep original values.

My question is how to update all the data at once and delete data individual such as subtaskdata, friendsdata or chatroomdata.

part of my serializer.py

class SubtaskDataSerializer(serializers.ModelSerializer):
    class Meta:
        model = SubtaskData
        fields = ("subtask_name","subtask_deadline","subtask_completion",
              "subtask_importance","subtask_item")
        depth = 3

class TaskDataSerializer(serializers.ModelSerializer):
    SubtaskDatas = SubtaskDataSerializer( many = True )
    class Meta:
        model = TaskData
        fields = ("task_name", "task_is_group",
              "task_time", "task_score", "task_member_list",
              "task_bulletin","SubtaskDatas")
        read_only_fields = ('SubtaskDatas',)
        depth = 2                

class FriendsDataSerializer(serializers.ModelSerializer):
    class Meta:
        model = FriendsData
        fields = ("friend_name","friend_account")
        depth = 2


class UserDataSerializer(serializers.ModelSerializer):
    TaskDatas = TaskDataSerializer( many = True )
    FriendsDatas = FriendsDataSerializer( many = True )
    ChatroomDatas = ChatroomDataSerializer( many = True )
    photo = Base64ImageField(
        max_length=None, use_url=True,
    )
    class Meta:
        model = UserData
        fields = ("pk","account","password","username","gender","score",
              "photo","TaskDatas","FriendsDatas","ChatroomDatas")
        read_only_fields = ('TaskDatas','FriendsDatas','ChatroomDatas',)
        depth = 1

views.py

@api_view(['GET','POST'])
def jobterm_list(request, format=None):

    if request.method=="GET":
        UserDatas =list(UserData.objects.all()) 
        serializer = UserDataSerializer(UserDatas,many=True)
        return Response(serializer.data)


    elif request.method == 'POST':
        serializer = UserDataSerializer(data=request.data)

        if serializer.is_valid():
            serializer.save()
            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 jobterm_detial(request,pk, format=None):
    try:
        User_Data = UserData.objects.get(pk=pk)
    except UserData.DoesNotExist:
        return Response(status=status.HTTP_404_NOT_FOUND)

    if request.method == "GET":
        serializer = UserDataSerializer(User_Data)
        return Response(serializer.data)

    elif request.method == "PUT":
        serializer = UserDataSerializer(User_Data,data=request.data)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data)
        else:
            return Response(serializer.errors,status=status.HTTP_400_BAD_REQUEST)

    elif request.method == "DELETE":
        User_Data.delete()
        return Response(status=status.HTTP_204_NO_CONTENT)

Answer 1

Finally, I try to define update() method accordingly like this.

def update(self, instance, validated_data):  
    instance.account = validated_data['account']
    instance.password = validated_data['password']
    instance.username = validated_data['username']
    instance.gender = validated_data['gender']
    instance.score = validated_data['score']
    instance.photo = validated_data['photo']

    Friends_Datas = User_Datas.get('FriendsDatas')
    for friend in Friends_Datas:
        friendsdatas, _ = FriendsData.objects.update_or_create(
            {'friend_name': friend.get('friend_name')},
            friend_account = friend.get('friend_account'),
            usersData_id = instance)

    Task_Datas = User_Datas.get('TaskDatas')
    for task in Task_Datas:
        taskdatas, _  = TaskData.objects.update_or_create(
            {
            'task_is_group' : task.get('task_is_group'),
            'task_time' : task.get('task_time'),
            'task_score' : task.get('task_score'),
            'task_member_list' : task.get('task_member_list'), 
            'task_bulletin' : task.get('task_bulletin'),   },
            task_name = task.get('task_name'),
            userData_id = instance
                                    )
        Subtask_Datas = task.get('SubtaskDatas')
        for subtask in Subtask_Datas:
            subtaskdatas = SubtaskData.objects.update_or_create(
                {'subtask_deadline' : subtask.get('subtask_deadline'), 
                'subtask_completion' : subtask.get('subtask_completion'), 
                'subtask_importance' : subtask.get('subtask_importance'), 
                'subtask_item' : subtask.get('subtask_item'), }
                ,subtask_name = subtask.get('subtask_name'), 
                taskData_id = taskdatas                
                                    )


    Chatroom_Datas = User_Datas.get('ChatroomDatas')
    for chatroom in Chatroom_Datas:
        chatroomdatas, _  = ChatroomData.objects.update_or_create(
            {'chatroom_contents' : chatroom.get('chatroom_contents'),},
            chatroom_member = chatroom.get('chatroom_member'), 
            userdata_cid = instance
             )

    return instance