How to write a custom decorator in django?

Question

The problem -

@is_premium_user
def sample_view:
          .......
          ......

I want certain views accesible to only the premium users of the website.
And how can I use this decorator across various applications in my project?

Answer 1

http://www.makina-corpus.org/blog/permission-required-decorator-django

i based mine off that blog post.

Stick that in a file in the python path or in a "util" app and import it into views:

e.g.

project_dir
|_ app1
|_ app2
|_ utils
   |_ __init__.py
   |_ permreq.py


from util.permreq import permission_required

@permmission_required('someapp.has_some_perm', template='denied.html')
def some_view(request):
    blah blah

Answer 2

Here is a slightly different implementation, which allows additional parameters in order to specify which page to redirect to when validation fails, and which message to display to the end user:

from functools import wraps
from django.core.urlresolvers import reverse
from django.http import HttpResponseRedirect
from core.helpers.flash import send_flash_error

def lender_only(redirect_to='plateforme.views.vue_login', error_flash_message=None):
  def inner_render(fn):
    @wraps(fn)  # Ensure the wrapped function keeps the same name as the view
    def wrapped(request, *args, **kwargs):
      if request.context.user.is_authenticated and request.context.user.is_lender:
        return fn(request, *args, **kwargs)
      else:
        if error_flash_message:
          send_flash_error(request, error_flash_message) # Replace by your own implementation

        return HttpResponseRedirect(reverse(redirect_to))
    return wrapped
  return inner_render

---

# Usage:
@lender_only('vitrine.views.projets', {'message': "Oops, can't go there."})
def render_page_index(request):

This guide helped me getting through it: https://elfsternberg.com/2009/11/20/python-decorators-with-arguments-with-bonus-django-goodness/ alongside the previous answers

Answer 3

Played around with the various links above and couldn't get them working and then came across this really simple one which I adapted. http://code.activestate.com/recipes/498217-custom-django-login_required-decorator/

from functools import wraps
from django.http import HttpResponseRedirect

def authors_only(function):
  @wraps(function)
  def wrap(request, *args, **kwargs):

        profile = request.user.get_profile()
        if profile.usertype == 'Author':
             return function(request, *args, **kwargs)
        else:
            return HttpResponseRedirect('/')

  return wrap

---

Using @wraps is better than manually overriding like doing wrap.__doc__ = fn.__doc__. Amongst other things, it ensures your wrapper function gets the same name as the wrapped function.

See https://docs.python.org/2/library/functools.html

Answer 4

Thanks to arie, the answer helped a long way, but it doesn't work for me.

When I found this snippet, I got it to work properly: http://djangosnippets.org/snippets/983/

This solution worked for me:

The helper function

This function has the benefit of being reusable in other places, as a drop in replacement for user.is_authenticated. It could for instance be exposed as a template tag.

def my_custom_authenticated(user):
    if user:
        if user.is_authenticated():
            return user.groups.filter(name=settings.MY_CUSTOM_GROUP_NAME).exists()
    return False

The decorator

I just put this at the top of my views.py, since it's so short.

def membership_required(fn=None):
    decorator = user_passes_test(my_custom_authenticated)
    if fn:
        return decorator(fn)
    return decorator

Using it

@membership_required
def some_view(request):
    ...

Answer 5

You don't have to write your own decorator for this as user_passes_test is already included in Django.

And there's a snippet (group_required_decorator) that extends this decorator and which should be pretty appropriate for your use case.

If you really want to write your own decorator then there's a lot of good documentation on the net.

And well, to (re-) use the decorator just put your decorator in a module on your path and you can import it from any other module.

Answer 6

See examples in django itself:

http://code.djangoproject.com/browser/django/trunk/django/contrib/auth/decorators.py

Your particular example is probably just a version of 'user_passes_test' where the test is going to be membership of the 'premium' group.

To use anywhere, make a python package and import it from there. As long as its on your sys.path it'll get found.