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?

Solution 1

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.

Solution 2

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

Solution 3

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):
    ...

Solution 4

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.

Solution 5

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

View more solutions

Comments

[dting]

You can write them into your models, docs.djangoproject.com/en/dev/topics/auth/#custom-permission‌​s and manage them through the admin or django shell

[user677990]

def souk_required(): """Requires user membership in at least one of the groups passed in.""" def has_souk(u): if u.is_authenticated(): if bool(SoukUsers.objects.get(person = u)): return True return False(u) return user_passes_test(has_souk)

[user677990]

it gives this error - souk_required takes no arguments (1 given)

[arie]

Hm .. i accidentally upvoted your comment ;-) Well, you removed the expected argument from you function definition and therefore receive the given error. So, what about creating a group "premiumusers" and adding your users to that group? Then you can use the snippet as it is and just pass in the name of your group.

[user677990]

Its not your fault it happens to the best of us ; ].... anyways thanks a lot man... I owe you an awful lot of time.

[radtek]

This should be the accepted answer, thumbs up! I tried to piggy back off the user_passes_test decorator but got lost, this saved the day.

[Ardian]

@radtek i got wrap() takes at least 1 argument (0 given). Any clue to solve it?

[radtek]

Would have to see your code, but most likely you didn't pass request to your function you are decorating.

[Sven]

the @wraps method is just for docs, so you could leave it out, right?