Django validate user request

Question

Im only a student and currently studying django. I have this in my Users/models.py

class Membership(models.Model):
membership_type = models.CharField(max_length=50)
price = models.IntegerField(default=100)
description = models.CharField(max_length=200)

def __str__(self):
    return self.membership_type





class Customer(models.Model):
user = models.OneToOneField(User, on_delete=models.CASCADE)
membership = models.ForeignKey(Membership, on_delete=models.CASCADE,null=True)
reference = models.CharField(max_length=50, null=True)

def __str__(self):
    return self.user.email

here's my views.py

def BookDetail(request, id):
most_recent = Book.objects.order_by('-timestamp')[:3]
user_membership = get_object_or_404(Customer, user=request.user)
book= get_object_or_404(Book, id=id)
form = CommentForm(request.POST or None)
if request.method == "POST":
    if form.is_valid():
        form.instance.user = request.user
        form.instance.post = book
        form.save()
        return redirect(reverse("book-detail", kwargs={
            'id': book.pk
        }))
context = {
    'user_membership': user_membership,
    'form': form,
    'book': book,
    'most_recent': most_recent,

}
return render(request, 'catalog/book_detail.html', context)

how do I validate the user if he/she is not part of Customer model in my book_detail.html (NOTE: EDITED)

       {% if request.user != user_membership.user %}
          <button class="site-btn" disabled="disabled">Read</button>
          {% else %}
          {% for content in book.pages %}
         <a href="{{ content.get_absolute_url }}" class="site-btn">Read</a>
          {% endfor %}
        {% endif %}

i'm having an error of "No Customer matches the given query.".. Uhm, i manually add user in Customer model in admin panel. it is not automatically added during registration(signals). but im ok with that.

Answer 1

You're using the context variable user_membership for your Customer object. That means you should use that name when looking up the Customer object in your template. For example:

{% if request.user != user_membership.user %}

In addition, you should also ensure that you have Django's request context processor set in your settings.py which allows you to use the request object in your template:

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': (
                'django.template.context_processors.request',
            ),
        }
    },
]

Update

If there is no Customer record configured for the current logged in user, then the code will currently return a 404 to the browser. However, if you wish to continue to render the template in this case, then you should modify the view so that it sets the user_membership variable to None:

def BookDetail(request, id):
    most_recent = Book.objects.order_by('-timestamp')[:3]
    try: 
        user_membership = Customer.objects.get(user=request.user)
    except Customer.DoesNotExist:
        user_membership = None

And then modify your template to check whether the user_membership is set:

{% if user_membership and user_membership.user == request.user %}
    {% for content in book.pages %}
        <a href="{{ content.get_absolute_url }}" class="site-btn">Read</a>
    {% endfor %}
{% else %}
    <button class="site-btn" disabled="disabled">Read</button>
{% endif %}