我对core.async还是很陌生，我一直试图了解如何最好地将core.async与文件IO结合使用。我整理了一个测试，尽管可以打印到控制台，但无法写入最后一个文件。知道我缺少什么吗？
首先，一些功能...
(defn thread-write-to-files [channel]
(let [writer (atom nil)]
(thread
(loop []
(when-some [value (<!! channel)]
(if (and (map? value) (= :FILE (:type value)))
(do (when @writer (.close ^Writer @writer))
(reset! writer (io/writer (File. ^String (:name value))))
(recur))
(do (when @writer (.write @writer value)
(println value))
(recur)))))
(when @writer
(do (.flush @writer)
(.close ^Writer @writer))))))
(defn add-line-number [channel-in channel-out]
(go-loop [line-number 1]
(when-some [value (<! channel-in)]
(if (and (map? value) (= :FILE (:type value)))
(do (>! channel-out value)
(recur 1))
(do (>! channel-out (str line-number ". " value))
(recur (inc line-number)))))))
现在使用它们的测试...
(deftest test-thread-write-to-file
(let [input-coll ["This gets skipped"
{:type :FILE :name "foo.txt"}
"This is the first line of foo!\n"
"This is the second line of foo.\n"
{:type :FILE :name "bar.txt"}
"Bar me 1.\n"
"Bar me 2.\n"
"Bar me 3.\n"
{:type :FILE :name "baz.txt"}
"BBBBBBBBBBB\n"
"AAAAAAAAAAA\n"
"ZZZZZZZZZZZ\n"]
input-channel (async/to-chan input-coll)
output-channel (chan)
foo (File. "foo.txt")
bar (File. "bar.txt")
baz (File. "baz.txt")]
(when (.exists foo) (.delete foo))
(when (.exists bar) (.delete bar))
(when (.exists baz) (.delete baz))
(add-line-number input-channel output-channel)
(thread-write-to-files output-channel)
(Thread/sleep 1000)
(is (.exists foo))
(is (.exists bar))
(is (.exists baz))
(is (> (.length foo) 0))
(is (> (.length bar) 0))
(is (> (.length baz) 0))))
最后测试的条件失败。文件baz.txt已创建，但为空。我的REPL从输入中打印出每一行，所以我对为什么文件仍然为空感到困惑。
最佳答案
在thread-write-to-files中，当输入通道关闭时(当(when-some [value (<!! channel)] ...)获得nil并退出loop时)，您将执行最终文件的刷新和关闭操作。
您的测试永远不会关闭通道，因此不会发生。尝试在close!上使用output-channel，或者也许使用 onto-chan 而不是to-chan将测试数据集合放入系统中。