iteration_async_example.cljc

;; An example usage of an imaginary `iteration-async` API, which uses
;; continuation passing to signal when to continue to the next page,
;; completion, and failure

(defn fetch-pages-async
  "Fetches summary pages repeatedly until no pages are left.
  Calls `done` callback when complete. Calls `err` if an error occurs."
  ([done err url]
   (fetch-summaries done err url 0))
  ([done err url page]
   (iteration-async
    (fn [cont fail page]
      (-> (js/fetch (str url "?page=" page))
          (.then #(.json %))
          ;; call `cont` callback with results to collect and continue fetching
          ;; the next page.
          ;; call `fail` callback if the request fails in some way
          (.then cont fail)))
    :kf :next-page
    :vf :data
    :initk page
    :somef some?
    :done done
    :error err)))

;; helper fns for when you are working strictly with promises or channels

(defn iteration-promise
  [pf & {:keys [kf vf initk somef]}]
  (js/Promise.
   (fn [resolve reject]
     (iteration-async pf :kf kf :vf vf :initk initk :somef somef :done resolve :error reject))))

(defn iteration-chan
  [vchan errchan & {:keys [kf vf somef]}]
  )