[FIXED] How to give data to ManyToManyField from view in django

Issue

Hello i am new to django and i am trying to create a page where we can add and participate in various events.

This is the model i created for my database

model.py

class Venue(models.Model):
    name = models.CharField('Venue Name', max_length=120)
    address = models.CharField(max_length=300)
    zip_code = models.CharField('Zip Code', max_length=6)
    phone = models.CharField('Contact Number', max_length=25, blank=True)
    web = models.URLField('Website Address', blank=True)
    email = models.EmailField('Email', blank=True)
    owner = models.IntegerField('Venue Owner', blank=False, default=1)
    venue_image = models.ImageField(null=True, blank=True, upload_to="images/")

class Event(models.Model):
    name = models.CharField('Event Name', max_length=120)
    event_date = models.DateTimeField('Event Date')
    venue = models.ForeignKey(Venue, blank=True,null=True, on_delete=models.CASCADE)
    manager = models.ForeignKey(User,blank=True,null=True,on_delete=models.SET_NULL)
    description = models.TextField(blank=True, )
    attendees = models.ManyToManyField(User,blank=True, related_name='attendees')

here i am trying to make a link by clicking that link user participate to that Event but i am not getting how to put the user data in the above attendees field

view function

def attendees(request):
    Event.attendees.add(request.user)
    return redirect('list-events')

error : AttributeError at /participate/ 'ManyToManyDescriptor' object has no attribute 'add'

link

<a href="{% url 'participate' %}">Participate</a>

url.py

path('participate/', attendees, name='participate')  

Solution

You need to specify for which event the user will be added, so the view should look like:

from django.contrib.auth.decorators import login_required
from django.shortcuts import get_object_or_404, redirect
from django.views.decorators.http import require_POST

@require_POST
@login_required
def attendees(request, pk):
    event = get_object_or_404(Event, pk=pk)
    event.attendees.add(request.user)
    return redirect('list-events')

participating should be done through a POST request since it alters entities. A GET request should only be used to retrieve data, not update it.

and the urls.py thus should contain a URL parameter for the primary key:

path('participate/<int:pk>/', attendees, name='participate')

Finally the template should thus make a POST request to the path with the primary key of the event:

<form method="post" action="{% url 'participate' pk=event.pk %}">
    <button type="submit">Participate</button>
<form>

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Note: You can limit views to a view to authenticated users with the @login_required decorator [Django-doc].

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Note: One can use the @require_POST decorator [Django-doc] to restrict the view to only be accessible for a POST request.

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Note: It is normally better to make use of the settings.AUTH_USER_MODEL [Django-doc] to refer to the user model, than to use the User model [Django-doc] directly. For more information you can see the referencing the User model section of the documentation.

Answered By - Willem Van Onsem