Question

我是Clojure的新手，我对嵌套的doseq循环有疑问。

我想迭代一个序列并得到一个子序列，然后得到一些键来在所有序列元素上应用一个函数。

给定的序列或多或少有这样的结构，但有数百本书籍，书架和许多图书馆：

([:state/libraries {6 #:library {:name "MUNICIPAL LIBRARY OF X" :id 6 
:shelves {3 #:shelf {:name "GREEN SHELF" :id 3 :books  
{45 #:book {:id 45 :name "NECRONOMICON" :pages {...}, 
{89 #:book {:id 89 :name "HOLY BIBLE" :pages {...}}}}}}}}])

这是我的代码：

(defn my-function []   (let [conn  (d/connect (-> my-system :config :datomic-uri))]
(doseq [library-seq (read-string (slurp "given-sequence.edn"))]
  (doseq [shelves-seq (val library-seq)]
    (library/create-shelf conn {:id (:shelf/id (val shelves-seq)) 
                                :name (:shelf/name (val shelves-seq))})
    (doseq [books-seq (:shelf/books (val shelves-seq))]
      (library/create-book conn (:shelf/id (val shelves-seq)) {:id (:book/id (val books-seq))
                                                               :name (:book/name (val books-seq))})
                                                               )))))

问题是我想要摆脱嵌套剂量混乱，但我不知道什么是最好的方法，因为在每次迭代中键都会改变。使用复发？降低？也许我正在考虑这种错误的方式？

Answer 1

就像Carcigenicate在评论中所说的那样，假设库/ ...函数只是副作用，你可以在一个doseq中写出来。

(defn my-function []
  (let [conn  (d/connect (-> my-system :config :datomic-uri))]
    (doseq [library-seq (read-string (slurp "given-sequence.edn"))
            shelves-seq (val library-seq)
            :let [_ (library/create-shelf conn
                                          {:id (:shelf/id (val shelves-seq))
                                           :name (:shelf/name (val shelves-seq))})]
            books-seq (:shelf/books (val shelves-seq))]
      (library/create-book conn
                           (:shelf/id (val shelves-seq))
                           {:id (:book/id (val books-seq))
                            :name (:book/name (val books-seq))}))))

我会分开＆＃34;连接到db＆＃34;来自＆＃34;啜饮文件＆＃34;来自＆＃34;写入db＆＃34;虽然。再加上一些解构，我最终会得到更多的东西：

(defn write-to-the-db [conn given-sequence]
  (doseq [library-seq given-sequence
          shelves-seq (val library-seq)
          :let [{shelf-id   :shelf/id,
                 shelf-name :shelf/name
                 books      :shelf/books} (val shelves-seq)
                _ (library/create-shelf conn {:id shelf-id, :name shelf-name})]
          {book-id :book/id, book-name :book/name} books]
    (library/create-book conn shelf-id {:id book-id, :name book-name})))

Clojure嵌套剂量循环

1 个答案: