Question

我正在研究一些Clojure代码，其中有一个像这样的实体树：

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

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

我要做的是生成一个哈希映射，其中键是 baz ID，值是 bar ID;即上图将是：

{"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"}
    ]}
  ]}
])

以下是构建baz-to-bar地图的代码：

(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)))])))

它有效，但非常迟钝。

有人可以在Clojure中建议一种更优雅，更有希望的惯用方法吗？

Answer 1

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

在Clojure中从分层树结构创建id的哈希映射的优雅方法

1 个答案: