有没有办法通知，当clojure未来完成？ [英] Is there a way to be notified when a clojure future finishes?

问题描述

有没有办法在未来设置手表，以便在完成后触发回调？

Is there a way to set a watch on a future so that it triggers a callback when it is done?

这样的东西？

> (def a (future (Thread/sleep 1000) "Hello World!")
> (when-done a (println @a))

...waits for 1sec...
;; =>  "Hello World"

推荐答案

您可以启动另一个任务来观察未来，然后运行该函数。在这种情况下，我将使用另一个未来，它很好地包装到一个when-done函数中：

You can start another task that watches the future and then runs the function. In this case I'll just use another future. Which wraps up nicely into a when-done function:

user=> (defn when-done [future-to-watch function-to-call] 
          (future (function-to-call @future-to-watch)))
user=> (def meaning-of-the-universe 
         (let [f (future (Thread/sleep 10000) 42)] 
            (when-done f #(println "future available and the answer is:" %)) 
            f))
#'user/meaning-of-the-universe

... waiting ...

user=> future available and the answer is: 42
user=> @meaning-of-the-universe
42

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