Om + DataScript

om_data.cljs

(ns om-data.core
  (:require [om.core :as om :include-macros true]
            [om.dom :as dom :include-macros true]
            [datascript :as d]))
 
(enable-console-print!)
 
(def schema {})
(def conn (d/create-conn schema))
 
;; prevent cursor-ification
(extend-type d/DB
  om/IToCursor
  (-to-cursor
    ([this _] this)
    ([this _ _] this)))
 
(d/transact! conn
  [{:db/id -1
    :title "Hello world!"
    :count 0}])
 
(defn get-conn [owner]
  (om/get-shared owner :conn))
 
(defn app-title [db]
  (ffirst
    (d/q
      '[:find ?title
        :where
        [?e :title ?title]]
      db)))
 
(defn app-count [db]
  (ffirst
    (d/q
      '[:find ?count
        :where
        [?e :count ?count]]
      db)))

(defn increment [e owner count]
  (d/transact! (get-conn owner)
    [[:db/add 1 :count (inc count)]]))
 
(defn app-view [db owner]
  (reify
    om/IRender
    (render [_]
      (let [count (app-count db)]
        (dom/div nil
          (dom/h2 nil (app-title db))
          (dom/div nil
            (dom/span nil count)
            (dom/button
              #js {:style #js {:marginLeft "5px"}
                   :onClick #(increment % owner count)}
              "+")))))))
 
(om/root app-view conn
  {:shared {:conn conn}
   :target (. js/document (getElementById "app"))})

I understand that this is a proof of concept, but presumably you would pass the db ref as a whole all the way down so that it can be queried. If so what are the implications (if any) on Om's functionality by not cursor-ifying db?

@afhammad By passing the db to om/root I believe the entire component tree is re-rendered on every change made to the db.

@scttnlsn I've tried following this with a more complex project, and it appears @afhammad is correct. You have to pass the db to all child components that you wish to respond to changes in the db.