CODEWITHSUNDEEP
pythonflask
Chris McKinnel
Chris McKinnel

Reputation: 15082

Passing a methods arguments to its parent classes constructor (Flask -- ModelView.as_view())

This is more of a general Python question than a Flask question.

This snippet of code comes from https://github.com/mitsuhiko/flask/blob/master/flask/views.py#L18.

@classmethod
def as_view(cls, name, *class_args, **class_kwargs):
    """Converts the class into an actual view function that can be used
    with the routing system.  Internally this generates a function on the
    fly which will instantiate the :class:`View` on each request and call
    the :meth:`dispatch_request` method on it.

    The arguments passed to :meth:`as_view` are forwarded to the
    constructor of the class.
    """
    def view(*args, **kwargs):
        self = view.view_class(*class_args, **class_kwargs)
        return self.dispatch_request(*args, **kwargs)

    if cls.decorators:
        view.__name__ = name
        view.__module__ = cls.__module__
        for decorator in cls.decorators:
            view = decorator(view)

    # we attach the view class to the view function for two reasons:
    # first of all it allows us to easily figure out what class-based
    # view this thing came from, secondly it's also used for instantiating
    # the view class so you can actually replace it with something else
    # for testing purposes and debugging.
    view.view_class = cls
    view.__name__ = name
    view.__doc__ = cls.__doc__
    view.__module__ = cls.__module__
    view.methods = cls.methods
    return view

Can somebody explain to me how exactly this as_view() function forwards its arguments to the constructor of the View class as it says it does in the method comment?

If not a direct explanation, maybe a shove in the right direction about specifically what I need to learn about Python-wise to better understand what is going on.

Thanks

Upvotes: 2

Views: 767

Answers (1)

Daniel Roseman
Daniel Roseman

Reputation: 599550

This line is the key one:

self = view.view_class(*class_args, **class_kwargs)

It's taking the arguments passed to as_view and using them to create an instance of view with those arguments.

Upvotes: 3

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