189 lines
6.6 KiB
Python
189 lines
6.6 KiB
Python
import typing as t
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from . import typing as ft
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from .globals import current_app
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from .globals import request
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http_method_funcs = frozenset(
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["get", "post", "head", "options", "delete", "put", "trace", "patch"]
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)
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class View:
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"""Subclass this class and override :meth:`dispatch_request` to
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create a generic class-based view. Call :meth:`as_view` to create a
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view function that creates an instance of the class with the given
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arguments and calls its ``dispatch_request`` method with any URL
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variables.
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See :doc:`views` for a detailed guide.
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.. code-block:: python
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class Hello(View):
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init_every_request = False
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def dispatch_request(self, name):
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return f"Hello, {name}!"
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app.add_url_rule(
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"/hello/<name>", view_func=Hello.as_view("hello")
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)
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Set :attr:`methods` on the class to change what methods the view
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accepts.
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Set :attr:`decorators` on the class to apply a list of decorators to
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the generated view function. Decorators applied to the class itself
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will not be applied to the generated view function!
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Set :attr:`init_every_request` to ``False`` for efficiency, unless
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you need to store request-global data on ``self``.
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"""
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#: The methods this view is registered for. Uses the same default
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#: (``["GET", "HEAD", "OPTIONS"]``) as ``route`` and
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#: ``add_url_rule`` by default.
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methods: t.ClassVar[t.Optional[t.Collection[str]]] = None
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#: Control whether the ``OPTIONS`` method is handled automatically.
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#: Uses the same default (``True``) as ``route`` and
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#: ``add_url_rule`` by default.
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provide_automatic_options: t.ClassVar[t.Optional[bool]] = None
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#: A list of decorators to apply, in order, to the generated view
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#: function. Remember that ``@decorator`` syntax is applied bottom
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#: to top, so the first decorator in the list would be the bottom
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#: decorator.
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#:
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#: .. versionadded:: 0.8
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decorators: t.ClassVar[t.List[t.Callable]] = []
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#: Create a new instance of this view class for every request by
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#: default. If a view subclass sets this to ``False``, the same
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#: instance is used for every request.
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#:
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#: A single instance is more efficient, especially if complex setup
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#: is done during init. However, storing data on ``self`` is no
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#: longer safe across requests, and :data:`~flask.g` should be used
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#: instead.
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#:
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#: .. versionadded:: 2.2
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init_every_request: t.ClassVar[bool] = True
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def dispatch_request(self) -> ft.ResponseReturnValue:
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"""The actual view function behavior. Subclasses must override
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this and return a valid response. Any variables from the URL
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rule are passed as keyword arguments.
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"""
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raise NotImplementedError()
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@classmethod
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def as_view(
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cls, name: str, *class_args: t.Any, **class_kwargs: t.Any
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) -> ft.RouteCallable:
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"""Convert the class into a view function that can be registered
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for a route.
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By default, the generated view will create a new instance of the
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view class for every request and call its
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:meth:`dispatch_request` method. If the view class sets
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:attr:`init_every_request` to ``False``, the same instance will
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be used for every request.
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The arguments passed to this method are forwarded to the view
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class ``__init__`` method.
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.. versionchanged:: 2.2
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Added the ``init_every_request`` class attribute.
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"""
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if cls.init_every_request:
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def view(**kwargs: t.Any) -> ft.ResponseReturnValue:
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self = view.view_class( # type: ignore[attr-defined]
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*class_args, **class_kwargs
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)
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return current_app.ensure_sync(self.dispatch_request)(**kwargs)
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else:
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self = cls(*class_args, **class_kwargs)
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def view(**kwargs: t.Any) -> ft.ResponseReturnValue:
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return current_app.ensure_sync(self.dispatch_request)(**kwargs)
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if cls.decorators:
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view.__name__ = name
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view.__module__ = cls.__module__
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for decorator in cls.decorators:
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view = decorator(view)
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# We attach the view class to the view function for two reasons:
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# first of all it allows us to easily figure out what class-based
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# view this thing came from, secondly it's also used for instantiating
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# the view class so you can actually replace it with something else
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# for testing purposes and debugging.
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view.view_class = cls # type: ignore
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view.__name__ = name
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view.__doc__ = cls.__doc__
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view.__module__ = cls.__module__
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view.methods = cls.methods # type: ignore
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view.provide_automatic_options = cls.provide_automatic_options # type: ignore
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return view
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class MethodView(View):
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"""Dispatches request methods to the corresponding instance methods.
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For example, if you implement a ``get`` method, it will be used to
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handle ``GET`` requests.
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This can be useful for defining a REST API.
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:attr:`methods` is automatically set based on the methods defined on
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the class.
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See :doc:`views` for a detailed guide.
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.. code-block:: python
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class CounterAPI(MethodView):
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def get(self):
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return str(session.get("counter", 0))
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def post(self):
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session["counter"] = session.get("counter", 0) + 1
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return redirect(url_for("counter"))
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app.add_url_rule(
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"/counter", view_func=CounterAPI.as_view("counter")
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)
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"""
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def __init_subclass__(cls, **kwargs: t.Any) -> None:
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super().__init_subclass__(**kwargs)
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if "methods" not in cls.__dict__:
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methods = set()
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for base in cls.__bases__:
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if getattr(base, "methods", None):
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methods.update(base.methods) # type: ignore[attr-defined]
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for key in http_method_funcs:
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if hasattr(cls, key):
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methods.add(key.upper())
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if methods:
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cls.methods = methods
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def dispatch_request(self, **kwargs: t.Any) -> ft.ResponseReturnValue:
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meth = getattr(self, request.method.lower(), None)
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# If the request method is HEAD and we don't have a handler for it
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# retry with GET.
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if meth is None and request.method == "HEAD":
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meth = getattr(self, "get", None)
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assert meth is not None, f"Unimplemented method {request.method!r}"
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return current_app.ensure_sync(meth)(**kwargs)
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