Reagent component util

reagent-component.cljs

(defn component
  "Experimental! A Reagent 'component' is a (fn [& [props children this]]) that:
    * May have special metadata for React lifecycle methods.
    * Returns either Hiccup data, or a nested (usu. post-setup) component[1].

  This util makes writing Reagent components a little more convenient:
    (component
      :render (fn [node_ & cmpt-args]) -> Hiccup data, or nested component[1].
      ;; Additional methods optional:
      :did-mount    (fn [node])
      :did-update   (fn [node])
      :will-unmount (fn [node]))
    -> (fn [& cmpt-args]) component.

  [1] Nb note that nested component fns are _only_ called when one or more of
      their input args have actually changed!!"

  [& lifecycle-methods]
  (let [methods (apply hash-map lifecycle-methods)
        node_   (atom nil)]
    (assert (ifn? (:render methods)) "No :render lifecycle method provided")
    (assert (every? #{:render :did-mount :did-update :will-unmount} (keys methods))
            "Bad lifecycle method key(s) provided")

    (with-meta
      (partial (:render methods) node_) ; [& cmpt-args] -> [node_ & cmpt-args]
      (merge methods

        ;; [rootNode] -> [node] + maintain node_:
        {:component-did-mount
         (fn [node*]
           ;; (debugf "component-did-mount: %s" node*)
           (let [node (reagent/dom-node node*)]
             (reset! node_ node)
             (when-let [mf (or (:component-did-mount methods)
                               (:did-mount methods))]
               (mf node))))}

        ;; [prevProps prevState rootNode] -> [node]:
        (when-let [mf (or (:component-did-update methods)
                          (:did-update methods))]
          {:component-did-update
           (fn [_ _ node*]
             ;; (debugf "component-did-update: %s" node*)
             (let [node (reagent/dom-node node*)]
               (mf node)))})

        ;; [] -> [node]:
        (when-let [mf (or (:component-will-unmount methods)
                          (:will-unmount methods))]
          {:component-will-unmount
           (fn []
             (let [node @node_]
               ;; (debugf "component-will-unmount: %s" node)
               (mf node)))})))))