How to pass url parameter to reverse_lazy in Django urls.py - django

Question

Consider that I have 1 resource and 2 urls (let's say new one and old one) connected to that resourse. So, i want to setup HTTP redirection for one of urls.
In myapp/urls.py I have:
urlpatterns = patterns('',
url(r'^(?P<param>\d+)/resource$',
'myapp.views.resource',
name='resource-view'
),
)
In mycoolapp/urls.py I want to specify:
from django.views.generic.simple import redirect_to
from django.core.urlresolvers import reverse_lazy
urlpatterns = patterns('',
url(r'^coolresource/(?P<param>\d+)/$',
redirect_to,
{
'url': reverse_lazy('resourse-view',
kwargs={'param': <???>},
current_app='myapp'
),
}
),
)
The question is how to pass <param> to the reverse_lazy kwargs (so, what to put instead of <???> in the example above)?

Answer 1

I wouldn't do this directly in the urls.py, I'd instead use the class-based RedirectView to calculate the view to redirect to:
from django.views.generic.base import RedirectView
from django.core.urlresolvers import reverse_lazy
class RedirectSomewhere(RedirectView):
def get_redirect_url(self, param):
return reverse_lazy('resource-view',
kwargs={'param': param},
current_app='myapp')
Then, in your urls.py you can do this:
urlpatterns = patterns('',
url(r'^coolresource/(?P<param>\d+)/$',
RedirectSomewhere.as_view()),
)

Answer 2

Redirect View is great if you are using a hard coded url, it replaced redirect_to which is now deprecated. I don't think you can use it when redirecting and reversing from urls.py. Here is my solution, x is the response object in this case:
from django.core.urlresolvers import reverse
from django.http import HttpResponseRedirect
urlpatterns = patterns('',
....
url(r'^coolresource/(?P<param>\d+)/$',
lambda x, param: HttpResponseRedirect(
reverse('myapp.views.resource', args=[param])
),
name='resource-view-redirect'),
....
)
You can still use the name of the url pattern instead of a hard coded url with this solution. The location_id parameter from the url is passed down to the lambda function.

Answer 3

As of Django 1.6 you can do this (Documentation):
...
from django.views.generic.base import RedirectView
urlpatterns = patterns('',
url(r'^coolresource/(?P<param>\d+)/$',
RedirectView.as_view(pattern_name='resource-view'),
),
)

Answer 4

One of the possible solutions of the general problem is to use hard-coded url pattern instead of reverse_lazy (documentation)
url(r'^coolresource/(?P<param>\d+)/$',
redirect_to,
{'url': '/%(param)s/resource'}
),
But, I don't like it so much, since it makes me harder after to do possible changes in urls.

Answer 5

You can't know or get what the value is until the view is called, so calculate url inside it.

Answer 6

Django's regex matching method for urls allows one to define and assign variables:
(?P<variable_name>...) defines variable_name depending on the uri being called; so what you need to put is: param instead of <???>