ClojureScript - assoc不是在承诺中工作

Question

我有一系列的艺术品。我想找出路线长度，并将其与每个艺术作品联系起来。

我的代码将如下所示：

(defn load-art-routes [art-list ctx]
 (doall (map-indexed (fn [index art]
   (let [user-location (select-keys (:coords (sub> ctx :geolocation)) [:latitude :longitude])
         art-location (:geoLocation art)]
       (->> (map-request {:origin (str (:latitude user-location) "," (:longitude user-location))
                     :destination (str (:lat art-location) "," (:lon art-location))
                     :mode (name (sub> ctx :transition-mode))})
             (p/map (fn [data]
                   (let [route-length (ocall js/Math "round" (/ (get-in data [:routes 0 :legs 0 :distance :value]) (* 0.621371192 1000)) 2)
                         route-duration (ocall js/Math "floor" (/ (get-in data [:routes 0 :legs 0 :duration :value]) 60))]
                     (js/console.log "load-art-routes route-length " route-length")
                     (assoc art :route-length route-length))))
             (p/error (fn [error]
                       (util/log (str "GOOGLE DIRECTIONS API ERRORS" params) error)
                       ))))) art-list))
                       art-list)
(defn map-request [params]
 (when params
   (let [endpoint google-directions-api-endpoint]
     (->> (make-get-req (str endpoint "&" (encode-query-params params))
                        {})
          (p/map (fn [data]
                   (util/log "GOOGLE DIRECTIONS API " data)
                   data))
          (p/error (fn [error]
                     (util/log (str "GOOGLE DIRECTIONS API ERRORS" params ) error)
                     ))))))

路由长度计算是正确的，但是assoc不工作。它实际上并没有关联它。我不知道问题出在哪里。有谁可以帮我？

Answer 1

请简化这个例子！在此过程中，您会发现问题所在。

首先，更新您的问题以包含显示p/map、p/error等是什么的require。此外，将map-request放在load-art-routes之前，就像它必须在源文件中一样。

然后，您应该从删除线程最后一个->>操作符开始，并使用带有中间值名称的let：

(let [aa (map-request ...)
      bb (p/map (fn [data] ...)   aa)
      cc (p/error (fn [error] ...) bb) ]
  <bb or cc here?> )

我怀疑您的p/error调用正在吞噬p/map的结果并返回nil。

Answer 2

这看起来像是你在尝试编写“可变”代码。

重新格式化代码并修复一个错误会使这一点变得更加明显：

(defn load-art-routes [art-list ctx]
  (doall (map-indexed (fn [index art]
                        (let [user-location (select-keys (:coords (sub> ctx :geolocation)) [:latitude :longitude])
                              art-location (:geoLocation art)]
                          (->> (map-request {:origin (str (:latitude user-location) "," (:longitude user-location))
                                             :destination (str (:lat art-location) "," (:lon art-location))
                                             :mode (name (sub> ctx :transition-mode))})
                               (p/map (fn [data]
                                        (let [route-length (ocall js/Math "round" (/ (get-in data [:routes 0 :legs 0 :distance :value]) (* 0.621371192 1000)) 2)
                                              route-duration (ocall js/Math "floor" (/ (get-in data [:routes 0 :legs 0 :duration :value]) 60))]
                                          (js/console.log "load-art-routes route-length " route-length)
                                          (assoc art :route-length route-length))))
                               (p/error (fn [error]
                                          (util/log (str " GOOGLE DIRECTIONS API ERRORS " params) error)
                                          ))))) art-list))
  art-list)

load-art-routes只是返回原始的art-list，并开始promises中的一些工作。这些承诺只更新它们的列表版本，但是考虑到我们使用的是不可变的数据结构，返回的art-list本身保持不变。p/error调用中是否还有可疑的第二个art-list？

您可能希望将其重新构造为返回一个Promise或接受一个回调，该回调在计算完所有route-length后将被调用。