How to pass cache objects between files?

[florimondmanca]

@invokermain wrote in #22:

A side question I had which would be nice to have documented: do you have a recommended way of passing cache objects to submodules (e.g. if you have various submodules defining a starlette router and some endpoints), or just around the project in general? Having some more example patterns in the documentation would be great 👍

[florimondmanca]

I think one possible idiom to use here is a resources.py file where you would declare the cache instance (or multiple instances, e.g. cache_default, cache_special, etc.), and then import it in the various parts of the application:

# project/resources.py
from caches import Cache

cache = Cache("locmem://null")

# project/apps/sub.py
from starlette.routing import Route
from ..resources import cache

async def view(request):
    item = await cache.get("some.key")
    ...

routes = [
    Route("/some/path", view),
]

# project/apps/main.py
from asgi_caches.middleware import CacheMiddleware
from starlette.applications import Starlette
from starlette.routing import Route, Mount
from starlette.middleware import Middleware
from ..resources import cache
from . import sub

async def home(request):
    ...

routes = [
    Route("/", home),
    Mount("/sub", routes=sub.routes),
]

middleware = [
    Middleware(CacheMiddleware, cache=cache),
]

app = Starlette(
    routes=routes,
    middleware=middleware,
    on_startup=[cache.connect],
    on_shutdown=[cache.disconnect],
)

(Note that I'm using the Starlette v0.13+ declarative style here.)