Django 2.2: Class-Based Views

def __init__(self, **kwargs):
    """
    Constructor. Called in the URLconf; can contain helpful extra
    keyword arguments, and other things.
    """
    # Go through keyword arguments, and either save their values to our
    # instance, or raise an error.
    for key, value in kwargs.items():
        setattr(self, key, value)

def _allowed_methods(self):
    return [m.upper() for m in self.http_method_names if hasattr(self, m)]

@classonlymethod
def as_view(cls, **initkwargs):
    """Main entry point for a request-response process."""
    for key in initkwargs:
        if key in cls.http_method_names:
            raise TypeError("You tried to pass in the %s method name as a "
                            "keyword argument to %s(). Don't do that."
                            % (key, cls.__name__))
        if not hasattr(cls, key):
            raise TypeError("%s() received an invalid keyword %r. as_view "
                            "only accepts arguments that are already "
                            "attributes of the class." % (cls.__name__, key))
    def view(request, *args, **kwargs):
        self = cls(**initkwargs)
        if hasattr(self, 'get') and not hasattr(self, 'head'):
            self.head = self.get
        self.setup(request, *args, **kwargs)
        if not hasattr(self, 'request'):
            raise AttributeError(
                "%s instance has no 'request' attribute. Did you override "
                "setup() and forget to call super()?" % cls.__name__
            )
        return self.dispatch(request, *args, **kwargs)
    view.view_class = cls
    view.view_initkwargs = initkwargs
    # take name and docstring from class
    update_wrapper(view, cls, updated=())
    # and possible attributes set by decorators
    # like csrf_exempt from dispatch
    update_wrapper(view, cls.dispatch, assigned=())
    return view

def form_invalid(self, form):
    """If the form is invalid, render the invalid form."""
    return self.render_to_response(self.get_context_data(form=form))

def get(self, request, *args, **kwargs):
    """Handle GET requests: instantiate a blank version of the form."""
    return self.render_to_response(self.get_context_data())

def get_form(self, form_class=None):
    """Return an instance of the form to be used in this view."""
    if form_class is None:
        form_class = self.get_form_class()
    return form_class(**self.get_form_kwargs())

def get_initial(self):
    """Return the initial data to use for forms on this view."""
    return self.initial.copy()

def get_prefix(self):
    """Return the prefix to use for forms."""
    return self.prefix

def get_redirect_url(self):
    """Return the user-originating redirect URL if it's safe."""
    redirect_to = self.request.POST.get(
        self.redirect_field_name,
        self.request.GET.get(self.redirect_field_name, '')
    )
    url_is_safe = is_safe_url(
        url=redirect_to,
        allowed_hosts=self.get_success_url_allowed_hosts(),
        require_https=self.request.is_secure(),
    )
    return redirect_to if url_is_safe else ''

def get_success_url_allowed_hosts(self):
    return {self.request.get_host(), *self.success_url_allowed_hosts}

def get_template_names(self):
    """
    Return a list of template names to be used for the request. Must return
    a list. May not be called if render_to_response() is overridden.
    """
    if self.template_name is None:
        raise ImproperlyConfigured(
            "TemplateResponseMixin requires either a definition of "
            "'template_name' or an implementation of 'get_template_names()'")
    else:
        return [self.template_name]

def http_method_not_allowed(self, request, *args, **kwargs):
    logger.warning(
        'Method Not Allowed (%s): %s', request.method, request.path,
        extra={'status_code': 405, 'request': request}
    )
    return HttpResponseNotAllowed(self._allowed_methods())

def options(self, request, *args, **kwargs):
    """Handle responding to requests for the OPTIONS HTTP verb."""
    response = HttpResponse()
    response['Allow'] = ', '.join(self._allowed_methods())
    response['Content-Length'] = '0'
    return response

def post(self, request, *args, **kwargs):
    """
    Handle POST requests: instantiate a form instance with the passed
    POST variables and then check if it's valid.
    """
    form = self.get_form()
    if form.is_valid():
        return self.form_valid(form)
    else:
        return self.form_invalid(form)

def put(self, *args, **kwargs):
    return self.post(*args, **kwargs)

def render_to_response(self, context, **response_kwargs):
    """
    Return a response, using the `response_class` for this view, with a
    template rendered with the given context.
    Pass response_kwargs to the constructor of the response class.
    """
    response_kwargs.setdefault('content_type', self.content_type)
    return self.response_class(
        request=self.request,
        template=self.get_template_names(),
        context=context,
        using=self.template_engine,
        **response_kwargs
    )

def setup(self, request, *args, **kwargs):
    """Initialize attributes shared by all view methods."""
    self.request = request
    self.args = args
    self.kwargs = kwargs