Class-Based Views

Class-based views are simply classes which implement response behaviour to requests. They provide a way to compartmentalise handling of different HTTP request types at the same endpoint. Rather than defining and decorating three different handler functions, one for each of an endpoint's supported request type, the endpoint can be assigned a class-based view.

Defining views

A class-based view should subclass HTTPMethodView. You can then implement class methods for every HTTP request type you want to support. If a request is received that has no defined method, a 405: Method not allowed response will be generated.

To register a class-based view on an endpoint, the app.add_route method is used. The first argument should be the defined class with the method as_view invoked, and the second should be the URL endpoint.

The available methods are get, post, put, patch, and delete. A class using all these methods would look like the following.

from sanic import Sanic
from sanic.views import HTTPMethodView
from sanic.response import text

app = Sanic('some_name')

class SimpleView(HTTPMethodView):

  def get(self, request):
      return text('I am get method')

  def post(self, request):
      return text('I am post method')

  def put(self, request):
      return text('I am put method')

  def patch(self, request):
      return text('I am patch method')

  def delete(self, request):
      return text('I am delete method')

app.add_route(SimpleView.as_view(), '/')

You can also use async syntax.

from sanic import Sanic
from sanic.views import HTTPMethodView
from sanic.response import text

app = Sanic('some_name')

class SimpleAsyncView(HTTPMethodView):

  async def get(self, request):
      return text('I am async get method')

app.add_route(SimpleAsyncView.as_view(), '/')

URL parameters

If you need any URL parameters, as discussed in the routing guide, include them in the method definition.

class NameView(HTTPMethodView):

  def get(self, request, name):
    return text('Hello {}'.format(name))

app.add_route(NameView.as_view(), '/<name>')

Decorators

If you want to add any decorators to the class, you can set the decorators class variable. These will be applied to the class when as_view is called.

class ViewWithDecorator(HTTPMethodView):
  decorators = [some_decorator_here]

  def get(self, request, name):
    return text('Hello I have a decorator')

  def post(self, request, name):
    return text("Hello I also have a decorator")

app.add_route(ViewWithDecorator.as_view(), '/url')

But if you just want to decorate some functions and not all functions, you can do as follows:

class ViewWithSomeDecorator(HTTPMethodView):

    @staticmethod
    @some_decorator_here
    def get(request, name):
        return text("Hello I have a decorator")

    def post(self, request, name):
        return text("Hello I don't have any decorators")

URL Building

If you wish to build a URL for an HTTPMethodView, remember that the class name will be the endpoint that you will pass into url_for. For example:

@app.route('/')
def index(request):
    url = app.url_for('SpecialClassView')
    return redirect(url)


class SpecialClassView(HTTPMethodView):
    def get(self, request):
        return text('Hello from the Special Class View!')


app.add_route(SpecialClassView.as_view(), '/special_class_view')

Using CompositionView

As an alternative to the HTTPMethodView, you can use CompositionView to move handler functions outside of the view class.

Handler functions for each supported HTTP method are defined elsewhere in the source, and then added to the view using the CompositionView.add method. The first parameter is a list of HTTP methods to handle (e.g. ['GET', 'POST']), and the second is the handler function. The following example shows CompositionView usage with both an external handler function and an inline lambda:

from sanic import Sanic
from sanic.views import CompositionView
from sanic.response import text

app = Sanic(__name__)

def get_handler(request):
    return text('I am a get method')

view = CompositionView()
view.add(['GET'], get_handler)
view.add(['POST', 'PUT'], lambda request: text('I am a post/put method'))

# Use the new view to handle requests to the base URL
app.add_route(view, '/')

Note: currently you cannot build a URL for a CompositionView using url_for.

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