That version has the unfortunate behavior that (func) can be interrupted if
(event) is called while it is running. Here's another version using an
agent:
(defn queue-with-delay2 [period func]
(let [q (agent nil)]
(fn []
(send-off q (fn [t]
(when t
(future-cancel t))
(future (Thread/sleep period) (send-off q (fn [_]
(func) nil))))))))
Running with a sleep to see that (func) is not canceled by subsequence
(event) calls:
(def event (queue-with-delay2 2000 #(do (println "running") (Thread/sleep
2000) (println "ending"))))
Oddly, if calling (event) between "running" and "ending" messages, the repl
will stack-overflow on the return value. No idea what that's about. But,
running like this is fine:
(do (event) nil)
On Monday, December 1, 2014 1:37:56 PM UTC-8, Brian Craft wrote:
>
> I have need to perform an action when a series of events is quiet for some
> period. That is, if one event arrives an action is queued to execute after
> some timeout. If a second event arrives the timeout is reset, and so-forth.
>
> The following code seems to work, however I'm wondering if calling
> 'future' from 'swap!' is a bad idea (side effecting), and if there's a
> better way.
>
> (defn queue-with-delay [period func]
> (let [f (atom nil)]
> (fn []
> (when @f
> (future-cancel @f))
> (swap! f (fn [_] (future (Thread/sleep period) (func)))))))
>
>
> Use like
>
> (def event (queue-with-delay 2000 #(println "running")))
> (event)
> (event)
> (event) ; pause 2 sec
> "running"
>
>
>
>
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