django 禁止直接分配到多对多集合的前向一侧。使用 user.set() 代替

Question

嗨，我在 django 中有一个项目，当我尝试运行服务器时，上面的消息显示这是 models.py fo

    class Display(models.Model) :
     url=models.URLField(unique=True)
     text = models.CharField(max_length=150) 
    
    class  Display_Data(models.Model) :
         displays = models.ManyToManyField(Display)  
         user= models.ManyToManyField(User)
         choosenum=models.IntegerField()
         puplish_date =models.DateTimeField(default=datetime.now) 
and this the view.py

tdef submit_operation(request):
 if request.method == 'POST':
    url = request.POST.get('url')
    text = request.POST.get('title')
    choosenum = request.POST.get('CHOOSE')

    if Display.objects.filter(url=url).exists():
        display = Display.objects.get(url=url)
        display_data = Display_Data.objects.create(choosenum=choosenum, user=request.user,                  date_published=datetime.now())
        display_data.displays.add(display)
    else:
        display = Display.objects.create(url=url, text=text)
        display_data = Display_Data.objects.create(choosenum=choosenum, user=request.user,    date_published=datetime.now())
        display_data.displays.add(display)        # ... (إعادة توجيه المستخدم)

    #return redirect('searchpage') 
    return redirect(request.META.get('HTTP_REFERER'))ype herea

`当我尝试引用在 abeer 上面的消息之前保存的视频时

i make a site show video from youtube in a frame and asked a user to value the vidio i saved vidio url and when i want from user to again evluate the vidio the mistake apeer

Answer 1

您看到此错误的原因是 不仅

displays

而且

user

字段也具有多对多关系。

在保存 [Display_Data] 之前，您无法将 [Display_Data] 与 [用户] 关联。

参考

因此，就像关联

displays

模型实例一样，您应该在创建并保存

user

模型实例后关联

display_data

实例。

您的模型.py：

class Display(models.Model) :
     url=models.URLField(unique=True)
     text = models.CharField(max_length=150) 

class Display_Data(models.Model) :
         displays = models.ManyToManyField(Display)  
         users = models.ManyToManyField(User)
         choosenum = models.IntegerField()
         puplish_date = models.DateTimeField(default=datetime.now) 

由于 m2m 字段

displays

是复数，为了保持一致性，我也将

users

字段设为复数

您的观点.py：

def submit_operation(request):
 if request.method == 'POST':
    url = request.POST.get('url')
    text = request.POST.get('title')
    choosenum = request.POST.get('CHOOSE')

    try:
        choosenum = int(choosenum)
    except e:
       raise ValueError("couldn't convert choosenum into int")
       # or you can handle the error in a way you like

    if Display.objects.filter(url=url).exists():
        display = Display.objects.get(url=url)
        display_data = Display_Data.objects.create(choosenum=choosenum, date_published=datetime.now())
        display_data.displays.add(display)
        display_data.users.add(request.user)
    else:
        display = Display.objects.create(url=url, text=text)
        display_data = Display_Data.objects.create(choosenum=choosenum, date_published=datetime.now())
        display_data.displays.add(display)        # ... (إعادة توجيه المستخدم)
        display_data.users.add(request.user)

    #return redirect('searchpage') 
    return redirect(request.META.get('HTTP_REFERER'))ype herea

还有：

在您的 models.py 上，您已将

choosenum

定义为整数字段：

choosenum = models.IntegerField()

但是

request.POST

中的所有数据都是字符串，所以你应该将其转换为整数：

choosenum = request.POST.get('CHOOSE')

try:
    choosenum = int(choosenum)
except e:
    raise ValueError("couldn't convert choosenum into int")
    # or you can handle the error in a way you like