om.next-datascript-problems.cljs

;; Context: I'm using datascript and representing a Component as an entity.
;; Discovered a few problems when trying to nest components.

;; Problem 1:
;; When this EntityComponent is updated, it tries to read :db/id :person/name 
;; and :person/likes.
;; Without context (like entity id in this case) those attributes may match many entries.
;;
;; Question:
;; Would it make sense to (assoc env :ident (ident c (props c))) in om/default-ui->props so
;; that (read ..) could get the ident of the component and use it as a look up ref:
(defui EntityComponent
  static om/IQuery
  (query [this]
    [:db/id :person/name :person/likes]) ;; <-- needs entity id when component wants to re-render?
  static om/Ident
  (ident [this {:keys [person/name]}]
    [:person/name name])) ;; <- datascript lookup ref

(defmulti read om/dispatch)
(defmethod read :default
  [{:keys [state ident selector]} key _]
  (let [sel (if selector {key selector} key)]
    {:value (d/pull (d/db state) [sel] ident)})) ;; <- using ident to find the state

;; Problem 2:
;; If a component does reverse lookups, like :person/_likes, the component is not 
;; re-rendered if the attribute :person/likes is changed, for example:
  [[:db/retract [:person/name "Petter"] :person/likes [:hobby :foosball]
;;
;; Question 2:
;; Would it make sense to let om.next know that :person/likes and :person/_likes 
;; are related, and re-render :person/_likes if :person/likes change?
  
(defui ReverseLookup
  static om/IQuery
  (query [this]
    [:db/id :hobby {:person/_likes (om/get-query EntityComponent)}])
  ..)

;; Thanks!
;; twitter: @petterik_