clojure - 为组件数据中缺少的键设置初始状态

Question

我正在努力学习 ClojureScript 和 Om。有一个具体案例让我在原地转圈。

我有一个在没有 key 的情况下首次呈现的组件。

(defn model-view [data owner]
  (reify
    om/IWillMount
    (will-mount [_]
      (om/transact! data [:stats] (fn [] {}))
      (go
        (let [response ((<! (api/get-stats (data :id))) :body)
              stats (:stats response)]
          (om/update! data [:stats] stats))))
    om/IRender
    (render [_]
      (dom/div nil
               (dom/h3 nil (data :title))
               ;; Here I want to use the :stats key in data that I
               ;; queried for in IWillMount, but its not present
               ;; the first time this model is rendered. It's only present
               ;; AFTER IWillMount has ran.
               (om/build model-stats-view (data :stats)))))

第一次调用此组件时，:stats 键根本不存在于 data 中。这就是为什么我调用 API 来获取其统计信息的原因。但 React 仍然调用 render 函数，因此组件崩溃。

我如何在此组件中设置一个初始状态，为 data 提供一个名为 :stats 的空映射，从而防止尝试呈现 nil在 (om/build model-stats-view) 调用中？

Answer 1

我更喜欢在初始化状态下进行所有初始化，然后在渲染状态下访问它。我在我的 did-mount 中放了一个 go-loop。当您在 go-loop 中更新您的初始状态(即:e-map)时，它会强制调用以渲染/重新渲染组件。我在我的所有组件中都使用它来进行组件间/组件内消息传递。只需将内容推送到发布/订阅 channel ，我们就可以开始比赛了。

;To update my state I use a function:

(defn set-owner-state! [owner old-map-key old-map new-map]
   (om/set-state! owner {old-map-key (merge old-map new-map)}))

om/IInitState
(init-state [_]
  (println "queue->init-state")
  {:e-map {:active-fsm nil}})

om/IDidMount
(did-mount [_]
    (go-loop []
        (let [[v _] (alts! [server-fsm-events dispatcher-events])
              current-state (om/get-state owner)
              e-map (:e-map current-state)]
        ; what goes in here is the logic to respond to a message
        ; in my case I have a match, it could be a cond or a set of
        ; if's.
        (set-owner-state! owner :e-map e-map {:active-fsm :active :task-paths nil})
    ...

om/IRenderState
(render-state [_ {:keys [e-map]}]
  (println "e-map:" e-map)
  ...