处理url参数类型的好方法是什么？

Question

Imagine an app with the following url.py :

urlpatterns = patterns('',
    url(r'^$', views.index),
    url(r'^double/(?P<number>\d+)/$', views.double),
)

And this views.py :

def double(request, number=42):
    return HttpResponse(2*number)

Obviously, I want number to be always taken as an int. When querying /double/5/ , I'll always expect to get 10 , not 55 .

Are there any good way to handle the parameters typing within Django urls?

Answer 1

Here's a decorator-based solution:

def param_type(**type_spec):
    def deco(f):
        def view(request, **kwargs):
            for k, type_ in type_spec.items():
                kwargs[k] = type_(kwargs[k])
            return f(request, **kwargs)
        return view
    return deco

@param_type(number=int)
def double(request, number=42):
    return HttpResponse(2*number)

Answer 2

This thread says that auto-conversion isn't a good solution:

Note that automatic conversion wouldn't be a good plan, either. For example, the next version of my blog converts URLs like 2008/2/25/ to 2008/02/25/ because I want a canonical form. So I need to know if \\d{1,2} matches one of two digits, even if the first one is 0. Auto-conversion to an integer would remove that capability (and it's not hard to think of other cases like this). So you'd need configurabiliy.

It also suggests a solution based on a decorator, but I'm not really convinced, it sounds a bit burdensome:

One solution to your problem could be to write a decorator that takes a list of types (plus something like None for "don't care") and automatically converts argument N to the type in the N-th element of the list before calling your function

Answer 3

Anto,

I think your question is more related to the url. (?P<number>\\d+) is a regular expression stating \\d only allowing digits it's the same as [0-9] . The + symbol tells it need 1 or more digits. So if you would try to insert something like double/notanumber/ it will not work.

Knowing this you can safely assume that:

1: number will always have a value

2: number will always be a integer (even that django gives it back as a unicode)

I made a small change to your function:

def double(request, number): # removed the =42 because number can never be empty
  return HttpResponse(2 * int(number)) # Converted your number to an integer