saved-ref.clj

(defn- save-agent [_ path data]
  (atomic-spit path data)
  (println (.getTime (Date.)) "wrote" path))

(defn saved-ref [path default]
  "Returns a ref backed by the file at path, with the default value if path could not be loaded"
  (let [value (read-string (clojure.contrib.duck-streams/slurp* path))
	r (ref (or value default))
	a (agent nil)]
    (add-watch r a (fn [_ _ _ new-val] (send-off a save-agent path new-val)))
    r))