Django View Preprocessing

Question

Just looking for some guidance here on how to implement this concept in "Django fashion".

I am using dbsettings to define site level variables. On each request I want to check one of my site level variables and render a different response based on the value of that variable.

Now I realize I could easily accomplish this just by adding a simple if statement in each of my view functions, but I thought there may be a way I could apply this at a higher level?

Let me know if there is a way to "globalize" this functionality across all requests. Thanks.

acjay · Accepted Answer · 2013-03-11 01:47:08Z

2

Actually, what you really probably want is middleware, if the setting is going to affect the template that's chosen in the first place, or substantially affect the response. It is a good deal more flexible than using a template context processor, which is more appropriate if you simply want to add a couple variables to your context.

You create a middleware.py in your app, which might contain something like:

from django.conf import settings

class MyMiddleware(object):
    def process_request(self, request):
        request.my_app_setting = settings.MY_APP_SETTING

Don't forget to add your class to your MIDDLEWARE_CLASSES setting.

answered Mar 11, 2013 at 1:47

acjay

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4 Comments

andersra Over a year ago

What are your thoughts on a custom view decorator?

acjay Over a year ago

Seems less DRY to me. You can take this with a grain of salt, but I personally would avoid decorators whenever they're not totally necessary. I love them, and they're a very powerful tool, but they can also make code much more mysterious. I see one, and I think, OK now this function could have just become anything under the sun. Middleware, on the other hand, is much more restricted in purpose to pretty much your exact sort of problem, with the drawback of a bit of being a bit "magical". But it's pretty well understood that random request attributes pretty much have to come from middleware.

andersra Over a year ago

With this middlewhere solution I don't see where you get the DRY advantage here. In the view I would still have to check the request.my_app_setting and then redirect appropriately no? Or can I check the value of request.my_app_setting in this MyMiddleware object, and redirect accordingly?

acjay Over a year ago

The difference is you don't have the same decorator on every view. If you use a decorator to populate one of the view's arguments, you still need to check it with an if. I'm not sure exactly what your situation is, but if the redirect is the same (or at least computable) if your setting is a certain variable, then you can just have the middleware return a response directly. That would be super DRY.

garnertb · Accepted Answer · 2013-03-11 01:38:13Z

0

You can use custom template context processors for passing "global" context to your views.

To accomplish this, create a new contextprocessors.py somewhere in your application with code similar to the example below (all it has to do is return a dict). Then add the path to the file with the function in the TEMPLATE_CONTEXT_PROCESSORS tuple in your settings.py (ie: yourapp.contextprocessors.resource_urls).

from django.conf import settings

def resource_urls(request):
    """Passes global values to templates."""

    return dict(
        TIME_ZONE = settings.TIME_ZONE,
    )

Now you can refer to these keys in your templates as expected: {{ TIME_ZONE }}.

answered Mar 11, 2013 at 1:38

garnertb

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