core.cljs

;; Tab-Menu scenario:
;; Show content based on a selected tab.
;; The reader is a simple datascript pull and :selected is a {:db/valueType :db.type/ref}.

;; Idea
;; If i could specify a component not to render if only a :db/id is received,
;; then i could simply pull and render - without the conditional logic in my render-fn.


(defn concat-queries [& args]
  (->> (apply concat args)
       distinct
       (into [])))

(defui TabMenu
       static om/IQuery
       (query [this]
              [{:selected (concat-queries [:db/id :image/title]  ;; subquery from image component: (om/get-query Image) in a real app.
                                          [:db/id :text/title]   ;; subquery from text component.
                                          [:db/id :video/title]}]) ;; subquery from video component.
              ;; this results in:
              ;;-> [{:selected [:db/id :image/title :text/title :video/title]}]                         
       Object
       (render [this]
               (let [props (:selected (om/props this)]
                 (dom/div nil
                   (some-> (:image/title props)
                           (image props)) ;; call component "image"
                   (some-> (:text/title props)
                           (text props))  ;; call component "text"
                   (some-> (:video/title props)
                           (video props))  ;; call component "video"
               ))))))

If I understand correctly you put in your DataScript the current selected ref under :selected.
So the the query [{:selected [:db/id :image/title :text/title :video/title]}] should return non nil value for the selected item ?