[Twisted-Python] Re: Resource.render() returning NOT_DONE_YET
bob at redivi.com
Mon Apr 28 13:11:33 EDT 2003
On Monday, Apr 28, 2003, at 12:17 America/New_York, Clark C. Evans
> On Mon, Apr 28, 2003 at 04:09:35PM +0000, Clark C. Evans wrote:
> | I was just giving a quick Twisted tutorial to someone using
> | twisted and as we were breaking page construction into more
> | than one chunk... an unexpected stumbling block occurred --
> | returning NOT_DONE_YET form the resource's render() function.
> | I was thinking about two other options:
> | 1. Perhaps NOT_DONE_YET could just be None, this
> | way, it can be the default return value. As I'm
> | browsing through my code this is the most common
> | return... why not make it the default.
> Err, this isn't exactly what I was thinking. What
> I was proposing... if during the scope of the render()
> function, req.write() is called, then a None value
> would be an allowable return. And if None is returned,
> req.finish() would be called automagically.
> | 2. Alternatively, allow a Deferred to be a return
> | value. Then the underlying caller can add
> | result.finish() to the deferred chain. This
> | has the advantage of not requiring finish() to
> | really be managed. Either the return value is
> | a string, a Deferred, (or for backwards compatibiliy
> | NOT_DONE_YET). In either of the primary cases,
> | result.finish() always gets called... thus making
> | it easier on newbies.
> | Ideally, both of the above options could be used...
Or, you could just deprecate NOT_DONE_YET and say "if you're doing
something that uses req.write you need to return a deferred".
For case 1, you return a deferred with an empty rval (None or '').
This signifies that you took care of req.write.
For case 2, you return a deferred with the page as the rval. This
signifies that you want the server to req.write.
I think that's the simplest way, and takes the return values for render
down to three, but really two for new code:
1) a string
2) a deferred
3) a deprecated NOT_DONE_YET
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