meander_search.clj

(require [meander.epsilon :as m])

(def test-data
  {:root
   {:first-child
    [{:inner-child
      [{:element "1"}
       {:element "2"}]}
     {:elements [{:element "3"}
                 {:element "4"}
                 {:nested-elements [{:element "5"}
                                    {:element "6"}]}]}]}})

(defn extract-key
  "Returns a sequence of values for given key k from nested map m"
  [k m]
  (->> (m/search m
         (m/$ {~k ?e})
         ?e)
       (filter identity)))

;; or same using postwalk and transients
(defn extract-key2
  "Returns a sequence of values for given key k from nested map m"
  [k m]
  (let [elements (transient [])]
    (walk/postwalk
     (fn [n]
       (when (and (vector? n) (= (first n) k))
         (conj! elements (second n)))
       n) m)
    (persistent! elements)))

(comment
  (->> (m/search test-data
         (m/$ {:element ?e})
         ?e)
       (filter identity))
  ;; => ("1" "2" "3" "4" "5" "6")
  
  (extract-key :element test-data)
  ;; => ("1" "2" "3" "4" "5" "6")

)