将clojure地图/数组写入文件并将其读回 [英] Writing clojure maps/arrays to a file and reading them back

问题描述

我需要将clojure地图保存到一个文件，稍后再读回来处理它们。

这是我能想出的。是否有更好的方法来完成同样的事情？

  user => （def my-data（for [a [Person1Person2] b [Address1Address2] 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/writermy-data.txt）] 
（doall n））xs））））
＃'user / write-data 
 
 user => （write-data my-data）
 
 user => （don（map＃（load-string％）（line-seq rdr）（def-read-data []（with-open [rdr（clojure.java.io/readermy-data.txt）] ）））））
＃'user / read-data 
 
 user => （count（read-data））
 40 
  

解决方案

p>从文件中读取单个表单最简单，所以我通常把我的数据放到一个向量中。
我也喜欢使用pr或 pr-str ，而不是打印，因为它保证产生可读的数据，

 （def my-data [{：afoo：b [1 2 3]}asdf42＃{1 2 3}]）
 spit/tmp/data.edn（with-out-str（pr my-data）））
 nil 
（read-string（slurp/tmp/data.edn））
 [{：afoo，：b [1 2 3]}asdf42＃{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}] 
  

注意字符串asdf是作为符号读回的。 / p>

.toString 也可正常工作：

 （spit/tmp/data.edn（.toString my-data））
（read-string（slurp/tmp/data.edn））
 [ {：afoo，：b [1 2 3]}asdf42＃{1 2 3}] 
  

I need to save clojure maps to a file and read them back later to process them.

This is what I could come up with. Is there a better way to accomplish the same thing?

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

解决方案

It is easiest to read a single form to and from the file, so I usually put my data into a vector. I also prefer to use pr or pr-str rather than print because it is guaranteed to produce readable data,

(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}] 

notice how the string `"asdf" was read back as a symbol.

.toString also works fine:

(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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