Clojure 深度合并以忽略 nil 值

Question

我正在尝试在Clojure中深度合并多个地图。我在网上找到了很多解决方案，其中大多数看起来像：

(defn deep-merge
  [& xs]
 (if (every? map? xs)
   (apply merge-with deep-merge xs)
  (last xs)))

这个解决方案的问题在于，如果其中一个映射为 nil，它将删除所有以前的映射（因此，如果最后一个映射为 nil，则整个函数将返回 nil）。在忽略 nil 值的常规合并函数中，情况并非如此。是否有其他忽略 nil 值的深度合并的简单实现？

Answer 1

我在以下位置找到了这个：https://github.com/circleci/frontend/blob/04701bd314731b6e2a75c40085d13471b696c939/src-cljs/frontend/utils.cljs。它完全符合它应该做的。

(defn deep-merge* [& maps]
  (let [f (fn [old new]
             (if (and (map? old) (map? new))
                 (merge-with deep-merge* old new)
                 new))]
    (if (every? map? maps)
      (apply merge-with f maps)
     (last maps))))
(defn deep-merge [& maps]
  (let [maps (filter identity maps)]
    (assert (every? map? maps))
   (apply merge-with deep-merge* maps)))

谢谢CircleCi人！

Answer 2

立即删除nil？

(defn deep-merge [& xs]
  (let [xs (remove nil? xs)]
    (if (every? map? xs)
      (apply merge-with deep-merge xs)
      (last xs))))