dbutils.cljs

(ns fncards.db.utils
  (:require [fncards.db.api :as db-api]
            [datascript :as ds]
            [cljs.pprint :refer [pprint]]
            [cljs.core.async :as async :refer [chan <! >! put! take! timeout mult tap pub sub]])
  (:require-macros [cljs.core.async.macros :refer [go go-loop]]
                   [fncards.macros :refer [log logr logd logc]]))

;; Channel and Subscription

(defn- build-handle-tx
  "On db update, put updated entity onto update-ch"
  [ch db]
  (fn
    [{:keys [tx-data]}]
    (let [id (-> tx-data first first)
          e (ds/entity @db (-> tx-data first first))]
      (if e (go (>! ch e))))))

(defn get-updates
  "Returns a channel that returns changes to db"
  [f]
  (let [db db-api/app-db
        entity-ch (chan)
        handle-tx (build-handle-tx entity-ch db)
        ch (chan)]
    (go-loop [entity false]
             (when entity
               (>! ch entity))
             (recur (f (<! entity-ch))))
    (ds/listen! db-api/app-db (keyword (gensym "get-update-fn")) handle-tx)
    ch))

useage.cljs

(ns fncards.db.views
  (:require
    [fncards.db.utils :as db-utils]
    [fncards.db.api :as db-api]
    [datascript :as ds]
    [cljs.pprint :refer [pprint]]
    [cljs.core.async :as async :refer [chan <! >! put! take! timeout mult tap pub sub]])
  (:require-macros [cljs.core.async.macros :refer [go go-loop]]
                   [fncards.macros :refer [log logr logd logc]]))

(defonce db db-api/app-db)

(defn updates []
  (db-utils/get-updates #(:view/current %)))

(defn change [k]
  (ds/transact! db [{:view/current k}]))