django-rest-framework如何决定`ModelViewSet`的默认`allowed_methods`应该是什么？

Question

The company I work for has 2 projects that use django and DRF 3.

• both projects have a ViewSet that extends ModelViewSet
• both ViewSets do not explicitly define the allowed_methods property and are just using whatever DRF figures should be the default
• both ViewSets do not override or define any handler methods ( create() , update() , partial_update() , patch() , etc.)

However, in one project the allowed_methods property defaults to [u'GET', u'PUT', u'PATCH', u'DELETE', u'HEAD', u'OPTIONS'] . For the other allowed_methods defaults to [u'GET', u'POST', u'HEAD', u'OPTIONS'] . Consequently, I get a 405 response with

Method "PATCH" not allowed.

when I attempt to send a PATCH request.

What causes project 2 to be more restricted?

Answer 1

DRF only exposes Django's internal _allowed_methods() so we should review the implementation of that method :

def _allowed_methods(self):
    return [m.upper() for m in self.http_method_names if hasattr(self, m)]

where self.http_method_names is defined as:

http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace']

Is there a difference in what methods these clases define that could explain what you're seeing?

Answer 2

The short answer:

In my case, I was accidentally sending my PATCH to the list URL, rather than the put/patch URL.

The longer answer:

I found that the problem isn't that one project has different defaults for allowed_methods , it's that the action_map and allowed_methods properties of the ViewSet change based on which of the ViewSet URLs you hit, since the action_map is influenced by the router (see SimpleRouter.routes ).

So if you try to hit "//[base_url]/your-model/" with PATCH or PUT , as I was doing, it will say that only ['GET', 'POST', 'HEAD', 'OPTIONS'] are allowed, and patch() will NOT be linked to partial_update() , even though it uses the same ViewSet class and partial_update() is present in that class.

If you want to send a PATCH , you have to send it to "//[base_url]/your-model/[some_id]/".