"Nathan" == Nathan <nathan.stocks@gmail.com> writes:
Nathan> Oh, ok. My apologies, Terry. Thanks - but no need! Nathan> After staring for awhile I think I figured out what's going on. Nathan> First, everywhere I use this method in real code is to provide a Nathan> final AMP response (which is why it works for me). I think what Nathan> Jean Paul meant was that the AMP code looks at the object that the Nathan> AMP responder returns, and if that object is a deferred, then the Nathan> underlying AMP code (that you don't normally see) waits for the Nathan> deferred's callback value and uses that as the actual return value Nathan> of the AMP responder. I've not looked at the code (maybe you should! :-)) but that sounds right. And it would probably do this by just adding another callback to the deferred. Nathan> I had mistakenly taken this as a more general method of Nathan> returned-deferreds-resolving-into-their-callback-values, which is Nathan> why everyone is taking issue with my hasty AMP-less pseudo-code. That sounds right. Nathan> I must say, I've had more trouble grasping the nuances of deferreds Nathan> and other twisted objects than any other framework or language I've Nathan> ever worked with. I also spend much more time _in vain_ going Nathan> through the docs and api reference than other languages. At least Nathan> there's a great mailing list! I know the feeling. I've found it helpful to read the various Deferred pages quite a few times through, to play with toy examples to see the flow of control, and also to read the source of defer.py (which isn't complex and which I think is elegant). Nathan> So back to my original task -- I'm trying to get that same behaviour Nathan> in AMP when using a deferred list -- but I could probably just create Nathan> a deferred and return it as the AMP response (because AMP will wait Nathan> for the deferred's callback value), and then fire a callback with my Nathan> correct answer once I've processed my deferred list. Thus, I could Nathan> avoid figuring out how AMP handles Nathan> deferred-lists-returned-from-responders altogether. That sounds right too. It might help to know that a DeferredList is just a subclass of Deferred. So when you return a DeferredList, you're in fact returning something that behaves like a regular Deferred. When its callback is fired, it gets a list of status & results from all the deferreds in the originally passed list. So if AMP knows how to handle deferreds, it can certainly handle a DeferredList too. Nathan> Have I got it straight now? Yep, sounds like it. Terry