如何使用统一命名空间的键获取地图的命名空间？

Question

Is there a way to get the namespace of a map with uniformly name spaced keys?

For example:

(map-ns {:some/key :val :some/other :val ,,,}) => “some”)

Answer 1

If the map is not empty and all of its keys have the same namespace, the following suffices:

(def map-ns (comp namespace first keys))

Alternatively:

(def map-ns (comp namespace ffirst))

And here is a version that returns nil when the map is empty or has keys with different namespaces:

(def map-ns
  (comp
    #(if-not (next %) (first %))
    distinct
    (partial map namespace)
    keys))

Alternatively:

(def map-ns
  (comp
    #(if-not (next %) (first %))
    distinct
    (partial map (comp namespace key))))

Answer 2

(->> m keys (map namespace) set)

上面将为您提供所有名称空间的集合，或者如果size> 1，则可以返回nil。