query-example.clj

(defn- filter-todos
  [todos current-filter]
  (case current-filter
    "SHOW_ALL" todos
    "SHOW_ACTIVE" (filter #(false? (:completed %1)) todos)
    "SHOW_COMPLETED" (filter #(true? (:completed %1)) todos)))

(defn- visible-todos-query
  [state [query-id]]
  (println "visible-todos-query called")
  (assert (= query-id :visible-todos))
  ;; "flatten", from
  ;; {:todos {:todos x :next-todo-id y} :filter z}
  (reaction (-> (get-in @state [:todos :todos])
                (filter-todos (:filter @state)))))