clojure - 在 Clojure 中从分层树结构创建 ids HashMap 的优雅方法

Question

我正在编写一些 Clojure 代码，其中有一个像这样的实体树:

foo1
 +-- bar1
 | +-- baz1
 | +-- baz2
 +-- bar2
   +-- baz3
foo2
 +-- bar3
   +-- baz4

如果我荒谬的 ASCII 艺术没有意义，我有一个 foos 列表，每个列表可以有零个或多个 bars，每个都可以有零个或多个bazes。

我想要做的是生成一个 HashMap ，其中键是baz ID，值是bar ID；即上图为:

{"baz1" "bar1", "baz2" "bar1", "baz3" "bar2", "baz4" "bar3"}

我的数据结构如下所示:

(def foos [
  {:id "foo1" :bars [
    {:id "bar1" :bazes [
      {:id "baz1"}
      {:id "baz2"}
    ]}
    {:id "bar2" :bazes [
      {:id "baz3"}
    ]}
  ]}
  {:id "foo2" :bars [
    {:id "bar3" :bazes [
      {:id "baz4"}
    ]}
  ]}
])

这是我构建 baz-to-bar map 的代码:

(defn- baz-to-bar [foos]
  (let [b2b-list (flatten (for [f foos] (flatten (for [bar (:bars c)] (flatten (for [baz (:bazes bar)] [(:id baz) (:id bar)]))))))
        b2b-map (if (not (empty? b2b-list)) (apply hash-map b2b-list))]
    (if b2b-map [:b2b (for [baz (keys b2b-map)] (entry-tag baz (b2b-map baz)))])))

它可以工作，但相当迟钝。

任何人都可以建议一种更优雅、希望更惯用的方式在 Clojure 中执行此操作吗？

Answer 1

(into {} (for [foo foos
               {bar-id :id :as bar} (:bars foo)
               {baz-id :id} (:bazes bar)]
           {baz-id bar-id}))