Registering API in apps

Question

With django-rest-framework I'm using the DefaultRouter

I want to provide APIs to several apps, so my question is can I do this in a django manner and put my router registrations in each app URLconf and have them appear either as one aggregate api or ideally in a namespaced way.

In other words if app1 contains modelA and modelB, while app2 contains modelC:

1. can I declare 2 routers that appear at mysite/app1/api and mysite/app2/api, or
2. can I have a single api at mysite/api which lists all three models yet register the individual models in their own app's urls.py

Something like

router = DefaultRouter()
router.register(r'users', views.UserViewSet)
router.register(include('app1.apis')
router.register(include('app2.apis')

Alternatively is there a simple way in which my router variable can be made available in each app's URLconf so that they can call router.register? I'm not sure if

urlpatterns = patterns('',
url(r'^snippets/', include('snippets.urls', namespace="snippets"))
...
url(r'^api/', include(router.urls)),

actually cause the code in app1/urls.py to be executed at that point so that it could call router.register somehow, so that the final url call includes all the app registrations as well as the project one.

UPDATE

Using a variation on Nicolas Cortot's option 2 I get my specific resource API to work, but it is not listed as an available resource in the root API at myserver\api\

I assume that somehow DefaultRouter creates it's own page definition and router.register adds entries to it. My current setup (and I think Nicholas's option 1 as well) create two separate routers, and only one can get displayed as the server root, with the setup below, myserver\api\ lists users but not snippets.

Here's my current setup:

project urls.py:

router = DefaultRouter()
router.register(r'users', views.UserViewSet)

urlpatterns = patterns('',
    url(r'^admin/', include(admin.site.urls)),
    url(r'^api/', include(router.urls)),
    url(r'^api/', include('snippets.apiurls')),
    url(r'^api-auth/', include('rest_framework.urls', namespace='rest_framework')),
)

project/snippets/apiurls.py:

router = DefaultRouter()
router.register(r'snippets', views.SnippetViewSet)

urlpatterns = patterns('',
    url(r'^', include(router.urls)),
)

If I reverse the order of the entries in the project urls.py as:

    url(r'^api/', include('snippets.apiurls')),
    url(r'^api/', include(router.urls)),

then I get snippets listed but not users

I guess Django is serving the first matching route.

Unless someone can tell me otherwise I seem to need a single router variable to be passed around and added to somehow.

Answer 1

Both options are possible. You can either expose the router or the urls in each app, and merge those into your global urls. I usually prefer using urls (option 2) because it gives more flexibility in each app: you can define extra non-api URLs as needed.

Option 1

In your global urls.py:

from app1.api.routers import router1
from app2.api.routers import router2

urlpatterns = patterns('',
    url(r'^snippets/', include('snippets.urls', namespace="snippets"))
    ...
    url(r'^app1/api/', include(router1.urls)),
    url(r'^app2/api/', include(router2.urls)),
)

You can as easily use the same endpoint for both routers (as long as you're careful not to use conflicting routes):

urlpatterns = patterns('',
    url(r'^snippets/', include('snippets.urls', namespace="snippets"))
    ...
    url(r'^api/', include(router1.urls)),
    url(r'^api/', include(router2.urls)),
)

Option 2

In appN/api/urls.py:

router = DefaultRouter()
router.register(r'users', views.UserViewSet)
router.register(include('app1.apis')

urlpatterns = patterns('',
    url(r'^', include(router.urls)),
    url(r'^misc/', some_other_view),
)

In your global urls.py:

urlpatterns = patterns('',
    url(r'^snippets/', include('snippets.urls', namespace="snippets"))
    ...
    url(r'^api/', include('app1.api.urls')),
    url(r'^api/', include('app2.api.urls')),
)

Note that the urls modules do not need to be the same as the urls for standard views.

Answer 2

This is possible by passing around a single router instance as follows.

Create a file called router.py or similar in your main project folder:

from rest_framework import routers
common_router = routers.DefaultRouter()

In each app's urls.py put:

from main.router import common_router as router
router.register(r'myapp-model-name', MyAppViewSet) 

In your main urls.py put:

import my_app1.urls  # to register urls with router
import my_app2.urls  # to register urls with router
...
# finally import router that includes all routes
from main.router import common_router

urlpatterns = [
    ...
    url(r'^api/', include(common_router.urls)),
    ...
]

Answer 3

To get all apps in the same API root, you need to register all your apps with the same DefaultRouter.

One way to achieve this is to make a custom router, which intercepts the register call and propagates it to a shared router. You then use this shared router to get the api urls.

class SharedAPIRootRouter(SimpleRouter):
    shared_router = DefaultRouter()

    def register(self, *args, **kwargs):
        self.shared_router.register(*args, **kwargs)
        super().register(*args, **kwargs)
        # if not py3: super(SharedAPIRootRouter, self).register(*args,**kwargs)

Then in each app:

# in app1/urls.py 
router = SharedAPIRootRouter()
router.register(r'app1', App1ModelViewSet)

# in app2/urls.py
router = SharedAPIRootRouter()
router.register(r'app2', App2ModelViewSet)

In your main urls.py, you must ensure you import the app urls so that registration occurs before we ask for shared_router.urls

import app1.urls
import app2.urls

def api_urls():
    return SharedAPIRootRouter.shared_router.urls

urlpatterns = patterns(
    '',
    url(r'^api/', include(api_urls())),   
)   

if you do not want to import the urls explicitly, you can do it by convention:

def api_urls():
    from importlib import import_module
    for app in settings.INSTALLED_APPS:
        try:
            import_module(app + '.urls')
        except (ImportError, AttributeError):
            pass
    return SharedAPIRootRouter.shared_router.urls

Answer 4

As a more advanced variant on @Grischa, I like to extend his approach:

In the main's routers.py:

from rest_framework import routers

api_v1_router = routers.SimpleRouter()

In the main's urls.py:

from django.urls import include, path

import app1.urls
from .routers import api_v1_router

# Register app urls
app1.urls.register(api_v1_router)
app2.urls.register(api_v1_router)
...

urlpatterns = [
    ...
    path('v1/', include((api_v1_router.urls, 'v1'))),
    ...
]

In each app's urls.py:

from main.routers import api_v1_router
from .apis import MyAppViewSet1, MyAppViewSet2


def register(router):
    router.register(r'myapp-model-name1', MyAppViewSet1)
    router.register(r'myapp-model-name2', MyAppViewSet2)

Two advantages of this approach:

1. You can control the registration of the apps in the main urls.py
2. The flexibility of register(router) allows you to register to different routers, for example when using both v1 and v2 for versioning.