合并地图而不覆盖键 [英] Merging maps without overriding keys

问题描述

我有一个clojure函数，它返回一键映射序列。我想将这些地图合并为一张地图；但是，如果有些地图具有相同的键，则我不想覆盖这些值，而只是将它们组合成一个向量。 合并似乎会覆盖，而与合并似乎会严重扭曲类型。

I have a clojure function that returns a sequence of 1-key maps. I want to merge these maps into one map; however, if there are maps with the same key, I don't want to overwrite the values, only to combine them into a vector. merge seems to overwrite, and merge-with seems to seriously distort the type.

我有：

({:foo "hello"}
 {:bar "world"} 
 {:baz "!!!"}
 {:ball {:a "abc", :b "123"}}
 {:ball {:a "def", :b "456"}}
 {:ball {:a "ghi", :b "789"}})

我想要：

{:foo "hello"
 :bar "world"
 :baz "!!!"
 :ball [{:a "abc", :b "123"} {:a "def", :b "456"} {:a "ghi", :b "789"}]}

谢谢。

推荐答案

(def data ...) ;; your list of maps

(apply merge-with (comp flatten vector) data)
;; => {:baz "!!!", :ball ({:b "123", :a "abc"} {:b "456", :a "def"} {:b "789", :a "ghi"}), :bar "world", :foo "hello"}

注意：在OP的情况下，可以使用 flatten ，但不是在创建属于冲突键的值向量时合并地图的一般方法。

Note: the use of flatten works in OP's case but is NOT a general way to merge maps while creating vectors of values belonging to colliding keys.

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