Blocking Deref Blog example

blockingderef.cljs

(defn blocking-deref
  "Given an atom and a Result object, attempt to cycle the process tick on derefing until `pred-fn` isn't true
By default, `pred-fn` is nil?
Once the condition doesn't hold, the Result will be set to @a, and @a is returned"
  ([a r]
   (blocking-deref a r nil?))
  ([a r pred-fn]
   (if (pred-fn @a)
     (node/process.nextTick #(blocking-deref a r pred-fn))
     (do (.setValue r @a)
       @a))))

configmap.cljs

;; This is the direct Result object you can use to access
;; a git config map
(def git-config-res
  (let [res (goog.result.SimpleResult.)]
    (->>
      (git-config-atom "user.email")
      (git-config-atom "user.name")
      ((fn [a] (blocking-deref a res #(< (count %) 2)))))
    res))

gitcore.cljs

(defn git-config-atom
  "Call the `git config` command to grab the value of a given key.
Return an atom that will hold the return/output string in a map {k output-value}.
Optionally pass in an atom (allowing you to build up many returns)"
  ([k]
   (git-config-atom k (atom {})))
  ([k ret]
   (do (sys-exec (str "git config --get " (name k))
                 (fn [_ out _]
                   (swap! ret assoc (keyword k) (cstr/trim out))))
   ret)))

main.cljs

(defn -main [& args]
  (let [git-root core/git-root-res
        git-conf core/git-config-res]
    (result/wait git-root
      #(binding [core/*repo-root* (.getValue git-root)]
         (result/wait git-conf
           (fn [] (main-control git-conf args)))))))