使用Clojure的core.async消耗文件内容

Consuming file contents with Clojure's core.async

我正在尝试使用Clojure的core.async库来消耗/处理文件中的行。当我的代码执行时，将抛出IOException: Stream closed。下面是一个REPL会话，它再现了与我的代码相同的问题：

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(require '[clojure.core.async :as async])
(require '[clojure.java.io :as io])

; my real code is a bit more involved with calls to drop, map, filter
; following line-seq
(def lines
(with-open [reader (io/reader"my-file.txt")]
(line-seq reader)))

(def ch
(let [c (async/chan)]
(async/go
(doseq [ln lines]
(async/>! c ln))
(async/close! c))
c))

; line that causes the error
; java.io.IOException: Stream closed
(async/<!! ch)

由于这是我第一次做这样的事情(异步+文件)，所以也许我对它应该如何工作有一些误解。有人可以说明将文件行发送到通道管道的正确方法是什么吗？

谢谢！

正如@Alan指出的那样，您对lines的定义将关闭文件而不读取其所有行，因为line-seq返回的是惰性序列。如果您扩展使用with-open宏...

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(macroexpand-1
'(with-open [reader (io/reader"my-file.txt")]
(line-seq reader)))

...您得到这个：

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(clojure.core/let [reader (io/reader"my-file.txt")]
(try
(clojure.core/with-open []
(line-seq reader))
(finally
(. reader clojure.core/close))))

您可以在完成文件读取后关闭文件，而不是立即关闭文件，以解决此问题：

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(def ch
(let [c (async/chan)]
(async/go
(with-open [reader (io/reader"my-file.txt")]
(doseq [ln (line-seq reader)]
(async/>! c ln)))
(async/close! c))
c))