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Routers and Sub-Applications ​

Nexios provides a powerful routing system that allows you to create modular and nested routing structures. Here's an example of how you can use routers and sub-applications in your application

🆕 Creating a Router and Mounting it to the Main Application ​

python
from nexios import NexiosApp
from nexios.routing import Router

app = NexiosApp()

v1_router = Router(prefix="/v1")

@v1_router.get("/users")
async def list_users(req, res):
    return res.json({"message": "List of users"})

@v1_router.get("/users/{user_id}")
async def get_user(req, res, user_id):
    return res.json({"user_id": user_id})

app.mount_router(v1_router)

Overriding Prefix at Mount Time You can override the default router prefix when mounting it to the app. This is helpful when reusing a router module in multiple places.

py
app.mount_router(v1_router, prefix="/api/v1")

Tip 💡

he prefix in mount_router always takes precedence over the one set in the Router instance.

This example creates a router with two routes, one for listing users and another for getting a specific user. The router is then mounted to the main application using the mount_router method.

This matches /v1/users and /v1/users/{user_id}

⚠️ Bug Alert

Ensure to use mount_router after all routes have been defined.

🤷‍♂️ What is Router? ​

A Router is a container for routes and sub-applications. It allows you to create a modular and nested routing structure in your application.

⚠️ Bug Alert

Ensure all mounted sub application or sub-routers have unique prefixes

Routers can contain other routers. This is useful when you want even finer modularization, e.g., versioned APIs with internal domains.

python

app = NexiosApp()

v1_router = Router(prefix="/v1")
user_router = Router(prefix="/users")

@user_router.get("/")
async def index(req, res):
    return res.text("User root")

@user_router.get("/{id}")
async def detail(req, res, id):
    return res.json({"user": id})

# Mount user_router inside v1_router
v1_router.mount_router(user_router)

# Mount v1_router into the app
app.mount_router(v1_router)

Now, the final paths are:

  • /v1/users/

  • /v1/users/{id}

You can nest as deeply as you want. Internally, Nexios flattens the route tree during app startup for performance.

The Router class also have similar routing methods as NexiosApp class

🌴 Sub-Applications = Routers ​

NexiosApp is a subclass of Router. This means you can treat entire apps as routers and mount them.

py
main_app = NexiosApp()
admin_app = NexiosApp()

@admin_app.get("/dashboard")
async def dashboard(req, res):
    return res.text("Welcome to the admin panel")

main_app.mount_router(admin_app, prefix="/admin")

Now you can access /admin/dashboard.

This makes it trivial to build modular applications where teams can work on separate parts (e.g., auth, billing, analytics) in isolation and plug them into a larger system