clojure.core.async/close!

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Type: function Added: Clojure unknown Examples: 2 Runnable: 0

([chan])

Closes a channel. The channel will no longer accept any puts (they will be ignored). Data in the channel remains available for taking, until exhausted, after which takes will return nil. If there are any pending takes, they will be dispatched with nil. Closing a closed channel is a no-op. Returns nil.

Logically closing happens after all puts have been delivered. Therefore, any blocked or parked puts will remain blocked/parked until a taker releases them.

Examples

by ertugrulcetin on 2018-03-16 . May have evaluation errors. ▶

(let [c (chan 2) ] (>!! c 1) (>!! c 2) (close! c) (println (<!! c)) ; 1 (println (<!! c)) ; 2 ;; since we closed the channel this will return false(we can no longer add values) (>!! c 1))

by nvseenu on 2022-03-09 . May have evaluation errors. ▶

;; Below example demonstrates go processes can take values (which were already put) ;; from the unbuffered channel even after closing it. (let [c (chan)] (go (>! c 1)) (go (>! c 2)) ;; channel is closed even before "2" value is taken out. (go (<! (timeout 5)) (close! c) (println "Channel closed")) (go (println (<! c))) ; 1 ;; Intentionally delaying the take operation so that channel can be closed ;; before. (go (<! (timeout 20)) (println (<! c)) ; We get 2 even though we tried to take after the channel ; is closed (println (<! c)))) ; nil since we dried out the channel and it is closed ; as well.

See also

• clojure.core.async/chan (0)

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