Om ref cursor not re-rendering components when updated

(ns ^:figwheel-always refs-test.core
(:require [om.core :as om :include-macros true]
          [om.dom :as dom :include-macros true]
          [sablono.core :as html :refer-macros [html]]))

(enable-console-print!)

(def app-state
  (atom {:items [{:text "cat"}
             {:text "dog"}
             {:text "bird"}]
     :selected-item {}}))

(defn selected-item []
  (om/ref-cursor (:selected-item (om/root-cursor app-state))))

(defn
  selected-item-title
  [_ owner]
  (reify
    om/IRender
    (render [_]
      (html
        [:div
        (let [selected (om/observe owner (selected-item))]
          (if (empty? selected)
            [:h1 "Nothing selected"]
            [:h1 (:text selected)]))]))))

 (defn
  selected-item-button
  [item owner]
  (reify
     om/IRender
    (render [_]
      (html
       [:li
        [:button {:on-click
                  (fn []
                    (om/update! (om/root-cursor app-state) :selected-item item)                      ;; this doesn't update
                    ;;(om/update! (om/root-cursor app-state) :selected-item (merge item {:foo 1}))   ;; this does
                  )} (:text item)]]))))

(defn
  root
  [cursor owner]
  (reify
    om/IRender
    (render [_]
      (html
       [:div
        (om/build selected-item-title {})
        [:ul
         (om/build-all selected-item-button (:items cursor))]]))))


    (om/root root app-state
      {:target (.getElementById js/document "app")})

(https://www.refheap.com/108491)

The (selected-item) function crerates a ref-cursor which tracks the :selected-item key in app-state. When you click a selected-item-button the title changes to reflect the new value that has been put into the map. However, this only works once. Pressing a different button does not cause the title to re-render again so the title is always stuck at the value of the first button you pressed.

Although, simply adding a merge with an additional keyword seems to make it work... (merging with an empty map doesn't work either, tried that!)

Is my understanding on ref cursors wrong?

Solution

So, the issue was very simple.

(om/update! (om/root-cursor app-state) :selected-item item)

should have been

(om/update! (om/root-cursor app-state) :selected-item @item)

Notice the item, because it's a cursor, is dereferenced.