update macro

gistfile1.clj

(defmacro defupdate
  [multi-fn dispatch-value & body-fn]
  `(. ~(with-meta multi-fn  {:tag 'clojure.lang.MultiFn})
      addMethod
      ~dispatch-value
      (fn [{:keys [action# verb# body#]}]
        (fn [channel# state#]
          (let [result# (apply ~@body-fn (state# body#))]
            (enqueue-and-close channel# (:response result#))
            (log/info "update" result#)
            result#)))))

(defmulti update :verb)
(defupdate update :add (fn [_ _] {:result nil :response nil}))

(. (with-meta update {:tag 'clojure.lang.MultiFn})
   addMethod
   :add
   (fn [{:keys [action verb body]}]
     (fn [channel state]
       (let [result (apply (fn [_ _] {:result nil :response nil}) (state body))]
         (enqueue-and-close channel (:response result))
         (log/info "update" result)
         result)))))