Class-Based Views ​

class flask.views.View ​

Subclass this class and override dispatch_request() to create a generic class-based view. Call as_view() to create a view function that creates an instance of the class with the given arguments and calls its · method with any URL variables.

See Class-based Views for a detailed guide.

class Hello(View):
    init_every_request = False

    def dispatch_request(self, name):
        return f"Hello, {name}!"

app.add_url_rule(
    "/hello/<name>", view_func=Hello.as_view("hello")
)

class Hello(View):
    init_every_request = False

    def dispatch_request(self, name):
        return f"Hello, {name}!"

app.add_url_rule(
    "/hello/<name>", view_func=Hello.as_view("hello")
)

Set methods on the class to change what methods the view accepts.

Set decorators on the class to apply a list of decorators to the generated view function. Decorators applied to the class itself will not be applied to the generated view function!

Set init_every_request to False for efficiency, unless you need to store request-global data on self.

• classmethod as_view(name, *class_args, **class_kwargs) ​

  Convert the class into a view function that can be registered for a route.

  By default, the generated view will create a new instance of the view class for every request and call its dispatch_request() method. If the view class sets init_every_request to False, the same instance will be used for every request.

  Except for name, all other arguments passed to this method are forwarded to the view class __init__ method.

  Changelog

  Changed in version 2.2: Added the init_every_request class attribute.

  Parameters:

  • name (str) –

  • class_args (t.Any) –

  • class_kwargs (t.Any) –

  Return type: ft.RouteCallable

• decorators: ClassVar[list[Callable]] = [] ​

• A list of decorators to apply, in order, to the generated view function. Remember that @decorator syntax is applied bottom to top, so the first decorator in the list would be the bottom decorator.

  Changelog

  New in version 0.8.

• dispatch_request() ​

  The actual view function behavior. Subclasses must override this and return a valid response. Any variables from the URL rule are passed as keyword arguments.

  Return type: ft.ResponseReturnValue

• init_every_request: ClassVar[bool] = True ​

  Create a new instance of this view class for every request by default. If a view subclass sets this to False, the same instance is used for every request.

  A single instance is more efficient, especially if complex setup is done during init. However, storing data on self is no longer safe across requests, and g should be used instead.

  Changelog

  New in version 2.2.

• methods: ClassVar[Collection[str] | None] = None ​

  The methods this view is registered for. Uses the same default (["GET", "HEAD", "OPTIONS"]) as route and add_url_rule by default.

• provide_automatic_options: ClassVar[bool | None] = None ​

  Control whether the OPTIONS method is handled automatically. Uses the same default (True) as route and add_url_rule by default.

class flask.views.MethodView ​

Dispatches request methods to the corresponding instance methods. For example, if you implement a get method, it will be used to handle GET requests.

This can be useful for defining a REST API.

methods is automatically set based on the methods defined on the class.

See Class-based Views for a detailed guide.

class CounterAPI(MethodView):
    def get(self):
        return str(session.get("counter", 0))

    def post(self):
        session["counter"] = session.get("counter", 0) + 1
        return redirect(url_for("counter"))

app.add_url_rule(
    "/counter", view_func=CounterAPI.as_view("counter")
)

class CounterAPI(MethodView):
    def get(self):
        return str(session.get("counter", 0))

    def post(self):
        session["counter"] = session.get("counter", 0) + 1
        return redirect(url_for("counter"))

app.add_url_rule(
    "/counter", view_func=CounterAPI.as_view("counter")
)

• dispatch_request(**kwargs) ​

The actual view function behavior. Subclasses must override this and return a valid response. Any variables from the URL rule are passed as keyword arguments.

Parameters:

• kwargs (t.Any) –

Return type: ft.ResponseReturnValue