In Joy of Clojure, there is a callback API to blocking API example in
the section on promises. Chouser outlines it a briefly in a
discussion on Promise/Deliver use cases here -
http://groups.google.com/group/clojure/browse_thread/thread/b1548aa40ba8072/210ec81bfe26032e?lnk=gst&q=promise#210ec81bfe26032e:
I've used them to convert a callback-based (continuation-passing
style, if you will) API into a blocking one. The lib I was using
provides something you can call like:
(rpc-call destination method-args done)
Where 'done' is a function that gets called with the results of
the remote procedure call. But I want to write a function that
does rpc but *returns* the result, so...
(let [p (promise)]
(rpc-call destination method-args #(deliver p %))
@p)
This will work just fine whether rpc-call calls 'done'
synchronously, or if it returns right away and 'done' is called
by some other thread later.
--Chouser
This is very neat. Is this robust as is or would you need to add code
to handle error cases such as an unavailable rpc server, rpc server
never returning, an error trying to make the rpc call, etc.
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