django Direct assignment to the forward side of a many-to-many set is prohibited. Use user.set() instead

Question

Hi I have a project in django when I try to runserver the message above is shown this is models.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)  
    user= models.ManyToManyField(User)
    choosenum=models.IntegerField()
    puplish_date =models.DateTimeField(default=datetime.now)

and this the views.py:

def 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

and when i try to refer to vidion saved before the message.

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

The reason as for why you are seeing this error is that not only displays but user field too has many-to-many relationship.

You can’t associate [Display_Data] with a [user] until [Display_Data] has been saved.

reference

So, just like you are associating your displays model instance, you should associate user instance after you have created and saved display_data model instance.

Your models.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) 

since m2m field displays is plural, I made users field plural as well for consistency

Your views.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

Also:

On your models.py your have defined choosenum as an integer field:

choosenum = models.IntegerField()

But all the data in request.POST is string, so you should convert it to integer:

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