Django 抛出 'Direct assignment to the forward side of a many-to-many set is prohibited.' 错误

Question

我在 Django 中有两个模型 Users和 Contexts .我已经定义了模型如下

class User(models.Model):
    userId = models.PositiveIntegerField(null = False)
    pic = models.ImageField(upload_to=getUserImagePath,null=True)
    Email = models.EmailField(null = True)

class Contexts(models.Model):
    context_name = models.CharField(max_length=50)
    context_description = models.TextField()
    context_priority = models.CharField(max_length=1)
    users = models.ManyToManyField(User, related_name='context_users')

现在我收到一个包含以下 JSON 的 POST 请求

{
"user" : 12,
"action" : "add",
"context_name": "Network debug",
"context_description" : "Group for debugging network issues",
"context_priority": "L"
}

我想在 Contexts中创建一个记录table.Below 是我想要做的

from django.shortcuts import render
from django.views.decorators.csrf import csrf_exempt
from django.http import HttpResponse
import json
from .models import *
import json


@csrf_exempt
def context_operation(request):
    if request.method == "POST":
        user_request = json.loads(request.body.decode('utf-8'))
        try:
            if user_request.get("action") == "add":
                conv = Contexts.objects.create(
                    context_name=user_request.get("context_name"),
                    context_description=user_request.get("context_description"),
                    context_priority=user_request.get("context_priority"),
                    users=user_request.get("user")
                )
                conv.save()
        except Exception as e:
            print("Context saving exception", e)
            return HttpResponse(0)
        return HttpResponse(1)

在这里，我尝试根据 JSON 请求中的 action 字段添加上下文。如您所见，在 Contexts 中模型、现场 users与 User 有多对多关系模型。但是当我尝试将值保存到 Contexts table 时，我收到以下错误

Context saving exception Direct assignment to the forward side of a many-to-many set is prohibited. Use users.set() instead.

基于 this StackOverflow post ，我尝试做这样的事情:

users=User.objects.add(user_request.get("user"))

但我仍然收到同样的错误。我究竟做错了什么？

Answer 1

错误应该是清楚的；您不能直接分配给多对多字段。创建项目后执行此操作。

conv = Contexts.objects.create(
    context_name=user_request.get("context_name"),
    context_description=user_request.get("context_description"),
    context_priority=user_request.get("context_priority"),
)
conv.users.add(user_request.get("user"))

另请注意，您不需要拨打 save()之后 create()或添加 m2m 值。