我需要将 clojure 映射保存到文件中并稍后读回以处理它们。
这就是我能想到的。有没有更好的方法来完成同样的事情?
user=> (def my-data (for [ a [ "Person1" "Person2" ] b [ "Address1" "Address2"] c (range 10) ] {:name a :address b :index c} ))
#'user/my-data
user=> (count my-data)
40
user=> (defn write-data[xs] (with-open [wrtr (clojure.java.io/writer "my-data.txt") ]
(doall (map #(.write wrtr (str % "\n")) xs))))
#'user/write-data
user=> (write-data my-data)
user=> (defn read-data[] (with-open [rdr (clojure.java.io/reader "my-data.txt") ]
(doall (map #(load-string %) (line-seq rdr)))))
#'user/read-data
user=> (count (read-data))
40
从文件中读取单个表单是最简单的,因此我通常将数据放入向量中。
我也更喜欢使用 pr 或pr-str
而不是打印,因为它保证产生可读的数据,
(def my-data [{:a "foo" :b [1 2 3]} "asdf" 42 #{1 2 3}])
(spit "/tmp/data.edn" (with-out-str (pr my-data)))
nil
(read-string (slurp "/tmp/data.edn"))
[{:a "foo", :b [1 2 3]} "asdf" 42 #{1 2 3}]
vs:
(spit "/tmp/data.edn" (with-out-str (print my-data)))
(read-string (slurp "/tmp/data.edn"))
[{:a foo, :b [1 2 3]} asdf 42 #{1 2 3}]
请注意字符串“asdf”是如何作为符号读回的。
.toString
也工作正常:
(spit "/tmp/data.edn" (.toString my-data))
(read-string (slurp "/tmp/data.edn"))
[{:a "foo", :b [1 2 3]} "asdf" 42 #{1 2 3}]
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