Let's say I have a map (m
) like this:
(def m {:a 1 :b 2 :c {:d 3 :e 4} :e { ... } ....})
I'd like to create a new map only containing :a
, :b
and :d
from m
, i.e. the result should be:
{:a 1 :b 2 :d 3}
I know that I can use select-keys
to easily get :a
and :b
:
(select-keys m [:a :b])
But what's a good way to also get :d
? I'm looking for something like this:
(select-keys* m [:a :b [:c :d]])
Does such a function exists in Clojure or what's the recommended approach?
In pure Clojure I would do it like this:
(defn select-keys* [m paths]
(into {} (map (fn [p]
[(last p) (get-in m p)]))
paths))
(select-keys* m [[:a] [:b] [:c :d]]) ;;=> {:a 1, :b 2, :d 3}
I prefer keeping the type of a path regular, so a sequence of keys for all paths. In clojure.spec
this would read as
(s/def ::nested-map (s/map-of keyword?
(s/or :num number? :map ::nested-map)))
(s/def ::path (s/coll-of keyword?))
(s/fdef select-keys*
:args (s/cat :m ::nested-map
:paths (s/coll-of ::path)))