Clojure: Get All Nested Map Values (N levels deep)
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Join For FreeI recently needed to pull all the values from a nested map. The map I was working with was designed to give easy access to data like so (formatted):
user=> (def my-data {"Jay" {"clojure" {:name "Jay", :language "clojure", :enjoys true}, "ruby" {:name "Jay", :language "ruby", :enjoys true}} "Jon" {"java" {:name "Jon", :language "java", :enjoys true}}} ) #'user/my-data user=> (get-in my-data ["Jon" "java"]) {:name "Jon", :language "java", :enjoys true} user=> (get-in my-data ["Jay" "ruby"]) {:name "Jay", :language "ruby", :enjoys true}This worked for all of the ways the data was accessed, until someone asked for a list of all people and all languages.
I needed a function that grabbed all the values nested to a point in the map (grabbing only the values instead of the deepest map wouldn't have provided valuable information). I created the following function that should grab all the values up to the nesting level specified.
(defn nth-vals* [a i m] (if (and (map? m) (> i 0)) (reduce into a (map (fn [v] (nth-vals* a (dec i) v)) (vals m))) (conj a m))) (defn nth-vals [i m] (if (nil? m) {} (nth-vals* [] i m)))The nth-vals function can be used as the following example shows. (assuming the same map for my-data) (formatted)
user=> (nth-vals 2 my-data) [{:name "Jay", :language "clojure", :enjoys true} {:name "Jay", :language "ruby", :enjoys true} {:name "Jon", :language "java", :enjoys true}]For reference, here's what's returned if we reduce the map all the way to it's values.
user=> (nth-vals 3 my-data) ["Jay" "clojure" true "Jay" "ruby" true "Jon" "java" true]That list of values may be helpful for someone else, but it wouldn't have solved our current problem.
And, if you're interested, here's what's returned if you ask for 1 level deep of values. (formatted, again)
user=> (nth-vals 1 my-data) [{"clojure" {:name "Jay", :language "clojure", :enjoys true}, "ruby" {:name "Jay", :language "ruby", :enjoys true}} {"java" {:name "Jon", :language "java", :enjoys true}}]I wouldn't at all be surprised if something like this already exists in Clojure core, but I haven't found it yet.
From http://blog.jayfields.com/2011/05/clojure-get-all-nested-map-values-n.html
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