ClojureScript-在go块中有条件地构造url

Question

I am using cemerick/url to construct my URL for an ajax request. However, some of the parameters of the query are coming from an asynchronous native callback. So I put everything in a go block, like the following :

(defn myFn [options]
  (go (let [options (cond-> options
                      ;; the asynchronous call
                      (= (:loc options) "getgeo") (assoc :loc (aget (<! (!geolocation)) "coords")))

            constructing the url
            url (-> "http://example.com"

                    (assoc-in [:query :param]  "a param")

                    ;; How do I not associate those if they don't exist ?
                    ;; I tried something along the lines of this, but it obviously doesn't work.
                    ;; (cond->  (and
                    ;;           (-> options :loc :latitude not-nil?)
                    ;;           (-> options :loc :latitude not-nil?))
                    ;;   (do
                    ;;     ))
                    ;; these will fail if there is no "latitude" or "longitude" in options
                    (assoc-in  [:query :lat] (aget (:loc options) "latitude"))
                    (assoc-in  [:query :lng] (aget (:loc options) "longitude"))

                    ;; url function from https://github.com/cemerick/url
                    (url "/subscribe")
                    str)])))

I would like to be able to be able to pass either {:loc "local} or {:loc {:latitude 12 :longitude 34}} or {} as a parameter to my function. I feel that I am not using the right structure already.

How I should construct this url ?

Answer 1

If I understood your question right, you require code, which looks like that:

;; helper function
(defn add-loc-to-url-as [url loc k as-k]
  (if-let [v (k loc)]
    (assoc-in url [:query as-k] v)
    url))

;; define function, that process options and extends URL
(defn add-location [url options]
  (if-let [location (:loc options)]
    (if (string? location)
      ;;; it expects string, for {:loc "San Francisco"}
      (assoc-in url [:query :location] location)
      ;;; or map, for {:loc {:latitude 12.123, :longitude 34.33}}
      (-> url
          (add-loc-to-url-as location :latitude :lat)
          (add-loc-to-url-as location :longitude :lng)))
    url))

;; now you can use it in your block
;; ...
the-url (-> (url "http://example.com" "subscribe")
            (assoc-in [:query :param] "a param")
            (add-location options))