multi_update.clj

(def alerts (atom {}))

(defn update-vals [mmap vals f]
  (reduce #(update-in % [%2] f) mmap vals))

(swap! alerts update-vals [:a :b :c] (fnil inc 0))

;d-std-alerts.core=> (swap! alerts update-vals [:a :b :c] inc)
;NullPointerException   [trace missing]

;dd-std-alerts.core=> (swap! alerts update-in [:a] (fnil inc 0))
;{:a 1}
;dd-std-alerts.core=> (swap! alerts update-in [:b] (fnil inc 0))
;{:b 1, :a 1}
;dd-std-alerts.core=> (swap! alerts update-in [:c] (fnil inc 0))
;{:c 1, :b 1, :a 1}
;dd-std-alerts.core=> (swap! alerts update-vals [:a :b :c] inc)
;{:c 2, :b 2, :a 2}