Class based views (#52)

* Renaming asgi_application, implementing CBV pattern, add_route method on router

* Refactor view to allow both sync/async methods

* Type hints for CBV

* Implement asgi decorator method directly in view class, remove classmethod

* Refactor CBV, remove router add_route method in favor of App.add_route method, tests, documentation

* Include tests

* Add support for class-based views

docs/views.md

@@ -0,0 +1,44 @@
+
+Starlette includes a `View` class that provides a class-based view pattern which
+handles HTTP method dispatching.
+
+The `View` class can be used as an other ASGI application:
+
+```python
+from starlette.response import PlainTextResponse
+from starlette.views import View
+
+
+class App(View):
+    async def get(self, request):
+        return PlainTextResponse(f"Hello, world!")
+```
+
+If you're using a Starlette application instance to handle routing, you can
+dispatch to a View class by using the `@app.route()` decorator, or the
+`app.add_route()` function. Make sure to dispatch to the class itself, rather
+than to an instance of the class:
+
+```python
+from starlette.app import App
+from starlette.response import PlainTextResponse
+from starlette.views import View
+
+
+app = App()
+
+
+@app.route("/")
+class Homepage(View):
+    async def get(self, request):
+        return PlainTextResponse(f"Hello, world!")
+
+
+@app.route("/{username}")
+class User(View):
+    async def get(self, request, username):
+        return PlainTextResponse(f"Hello, {username}")
+```
+
+Class-based views will respond with "406 Method not allowed" responses for any
+request methods which do not map to a corresponding handler.

mkdocs.yml

@@ -18,6 +18,7 @@ nav:
     - Applications: 'applications.md'
     - Test Client: 'test_client.md'
     - Debugging: 'debugging.md'
+    - Views: 'views.md'
 
 markdown_extensions:
   - markdown.extensions.codehilite:

starlette/app.py

@@ -3,6 +3,7 @@ from starlette.routing import Path, PathPrefix, Router
 from starlette.types import ASGIApp, ASGIInstance, Receive, Scope, Send
 from starlette.websockets import WebSocketSession
 import asyncio
+import inspect
 
 
 def request_response(func):
@@ -52,24 +53,32 @@ class App:
         self.router.routes.append(prefix)
 
     def add_route(self, path: str, route, methods=None) -> None:
-        if methods is None:
-            methods = ["GET"]
-        instance = Path(path, request_response(route), protocol="http", methods=methods)
+        if not inspect.isclass(route):
+            route = request_response(route)
+            if methods is None:
+                methods = ["GET"]
+
+        instance = Path(path, route, protocol="http", methods=methods)
         self.router.routes.append(instance)
 
     def add_websocket_route(self, path: str, route) -> None:
-        instance = Path(path, websocket_session(route), protocol="websocket")
+        if not inspect.isclass(route):
+            route = websocket_session(route)
+
+        instance = Path(path, route, protocol="websocket")
         self.router.routes.append(instance)
 
     def route(self, path: str):
         def decorator(func):
             self.add_route(path, func)
+            return func
 
         return decorator
 
     def websocket_route(self, path: str):
         def decorator(func):
             self.add_websocket_route(path, func)
+            return func
 
         return decorator
 

starlette/views.py

@@ -0,0 +1,22 @@
+from starlette.request import Request
+from starlette.response import Response, PlainTextResponse
+from starlette.types import Receive, Send, Scope
+
+
+class View:
+    def __init__(self, scope: Scope):
+        self.scope = scope
+
+    async def __call__(self, receive: Receive, send: Send):
+        request = Request(self.scope, receive=receive)
+        kwargs = self.scope.get("kwargs", {})
+        response = await self.dispatch(request, **kwargs)
+        await response(receive, send)
+
+    async def dispatch(self, request: Request, **kwargs) -> Response:
+        handler_name = "get" if request.method == "HEAD" else request.method.lower()
+        handler = getattr(self, handler_name, self.method_not_allowed)
+        return await handler(request, **kwargs)
+
+    async def method_not_allowed(self, request: Request, **kwargs) -> Response:
+        return PlainTextResponse("Method not allowed", 406)

tests/test_views.py

@@ -0,0 +1,38 @@
+import pytest
+from starlette import App
+from starlette.views import View
+from starlette.response import PlainTextResponse
+from starlette.testclient import TestClient
+
+
+app = App()
+
+
+@app.route("/")
+@app.route("/{username}")
+class Homepage(View):
+    async def get(self, request, username=None):
+        if username is None:
+            return PlainTextResponse("Hello, world!")
+        return PlainTextResponse(f"Hello, {username}!")
+
+
+client = TestClient(app)
+
+
+def test_route():
+    response = client.get("/")
+    assert response.status_code == 200
+    assert response.text == "Hello, world!"
+
+
+def test_route_kwargs():
+    response = client.get("/tomchristie")
+    assert response.status_code == 200
+    assert response.text == "Hello, tomchristie!"
+
+
+def test_route_method():
+    response = client.post("/")
+    assert response.status_code == 406
+    assert response.text == "Method not allowed"