compare.clj

;; Bogey (sets the :current boolean for each player)
(defn select-player [app player]
  (om/transact! app :players (fn [players]
                               (mapv (fn [p]
                                       (assoc p :current (= p @player)))
                                     players))))

;; Birdie -- but I feel like it's more cognitive load
(defn select-player [app player]
  (let [set-current #(assoc % :current (= % @player))]
    (om/transact! app :players #(mapv set-current %))))

; NOTE: See core.cljs for the usage with (partial select-player app player). That part is cool.