[Twisted-web] Using deferreds to render a page
grant at osafoundation.org
Mon Dec 5 11:27:40 MST 2005
On Dec 5, 2005, at 10:16 , A. Goryunov wrote:
> I might be just dumb, but I can't figure out the correct way to do
> what the following passage from Twisted.web's Howto suggests:
> "/Request a |Deferred|, return |server.NOT_DONE_YET|, and call |
> request.write("stuff")| and |request.finish()| later, in a callback
> on the |Deferred|/."
> How do I get at the request object from a callback function? All
> the documentation on Deferreds that I managed to find uses print's
> to display results, but that doesn't help any, since I intend to
> present output to a remote user rather than myself. For now I've
> settled with using the following method:
> class PrintResult(object):
> def __init__(self, request):
> self.request = request
> def __call__(self, *args):
> l = args
> if l:
> self.request.write("<html>ID is %s</html>" % str(l))
> self.request.write( "<html>No ID found</html>")
> return server.NOT_DONE_YET
> So that the request is stored inside the callback itself, but this
> somehow feels wrong. Is there some standard way of doing this that
> I am missing?
One way is to define the callback within the scope of request (and
self, your Resource), and let Python do the rest for you. E.g.
def render_GET(self, request):
# .... do something interesting with result ...
d = self.makeADeferred(request)
d.addCallback(finishUp) # You also need an errback here!
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