Find Value of Specific Key in Nested Map

Question

In Clojure, how can I find the value of a key that may be deep in a nested map structure? For example:

(def m {:a {:b \"b\"
            :c \"c\"
            :d {         


        

Answer 1

If you know the "path", consider using get-in:

(get-in m [:a :d :f]) ; => "f"

If the "path" is unknown you can use something like next function:

(defn find-in [m k]
  (if (map? m)
    (let [v (m k)]
      (->> m
           vals
           (map #(find-in % k)) ; Search in "child" maps
           (cons v) ; Add result from current level
           (filter (complement nil?))
           first))))

(find-in m :f) ; "f"
(find-in m :d) ; {:e "e", :f "f"}

Note: given function will find only the first occurrence.