Question

我试图在Clojure中深度合并多个地图。我在网上找到了很多解决方案，其中大部分都是这样的：

(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，如果其中一个地图是nil，它将删除所有先前的地图（因此如果最后一个地图为nil，则整个函数将返回nil）。在常规合并函数中不是这种情况，它忽略了nil值。是否有任何其他简单的深度合并实现忽略了零值？

Answer 1

我在https://github.com/circleci/frontend/blob/04701bd314731b6e2a75c40085d13471b696c939/src-cljs/frontend/utils.cljs找到了这个。它完全符合它的要求。

(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))))

Clojure深度合并以忽略nil值

2 个答案: