在视图后执行的金字塔中添加功能

Question

How do I add code to my pyramid app that is executed after the code in the view?

I need to do something to my beaker session before and after the view code. Before is no problem, I use a @subscriber(NewRequest) . All the ways I tried so far seem to happen too late (values I write to the session do not seem to be saved, although code is executed, as I can see in the log).

I tried putting it in a @subscriber(BeforeRender) , a @subscriber(NewResponse) , and in a finished callback I add in the NewRequest : event.request.add_finished_callback(finished_callback) – None of the values I write to the session stick. Only the one I added as last line in the view handler does (but I will not write that line in all of my views).

The pyramid docs on NewResponse state:

Postprocessing a response is usually better handled in a WSGI middleware component than in subscriber code that is called by a pyramid.interfaces.INewResponse event. [...]

But I'm lost on that, since I don't know wsgi that well and trying to find a spot to enter via google did not point my anywhere.

Answer 1

Got my solution from the answer by @MikkoOhtamaa, but I wanted the code to be on this page, so here is what I did with some explanation:

This can be achieved with a tween. That is a function (or other callable), that is called instead of the view and gets the job of calling the view, so you can do stuff just before and after the call. Using this I got rid of the @subscriber(NewRequest) as well and put it all in one place. Imagine this in your projects main init .py, where you create the wsgi-app. The project's name would be myapp .

def values_tween_factory(handler, registry):
    """
    Factory for creating the tween that wraps around the view.
    """
    def values_tween(request):
        """
        This is called in stead of the view with the view as param.
        """
        # do stuff before view code with request and session
        request.some_values = request.session.get('stored_values', [])
        # execute the view, creates the response
        response = handler(request)
        # do stuff after the view code with request and session
        request.session['stored_values'] = request.some_values
        # return the response returned by the view
        return response

    # return the new tween
    return state_tween

# [... other module level stuff ...]


def main(global_config, **settings):
    """
    The main function creating the wsgi-app.
    """
    config = Configurator(settings=settings)

    # [...] other stuff, like DB

    # register the tween - must be done by dotted name
    config.add_tween('myapp.values_tween_factory')

    # ... do more other stuff

    application = config.make_wsgi_app()
    # done - return created application object:
    return application

Answer 2

Tweens （be-tween）允许您在每个请求之前和之后执行代码。