Use the first key in a map as the dispatch value for defmulti

defmulti_key_as_dispatch_value.clj

; Example of using the first key in a map as the dispatch value for defmulti

(defmulti foo (fn [x] (first (map key x))) )

(defmethod foo :a [x] ["a -> " x])
(defmethod foo :b [x] ["b -> " x])
(defmethod foo :default [x] ["default -> " x])

(println (foo {:a "a"}))
(println (foo {:b "b"}))
(println (foo {:c "c"}))
(println (foo {:d "d"}))

; returns
;[a ->  {:a a}]
;[b ->  {:b b}]
;[default ->  {:c c}]
;[default ->  {:d d}]