Hi @vlaaad, I'm trying to update a label while and after another button-triggered operation takes place. Eg. displaying "Loading" and "Done". I got inspired by (copied) parts of   https://github.com/cljfx/cljfx/blob/master/examples/e18_pure_event_handling.clj .

;; Option 1. Dispatching two events (as per the conversation a few weeks ago)
(defmethod handler-fn ::entrypoint1 [{:keys [fx/context]}]
  (let [config (fx/sub-val context :config)]
    [[:dispatch {:event-type ::loading-status}]
     [:dispatch {:event-type ::processing
                 :config config}]]))

;; Option 2. Single dispatch, passing also a :context key to wrap-effects
(defmethod handler-fn ::entrypoint2 [{:keys [fx/context]}]
  (let [config (fx/sub-val context :config)]
    {:dispatch {:event-type ::processing
                 :config config}
     :context (fx/swap-context context assoc :status "Loading...")}))

(defmethod handler-fn ::loading-status [{:keys [fx/context]}]
  {:context (fx/swap-context context assoc :status "Loading...")})

(defmethod handler-fn ::success-status [{:keys [fx/context]}]
  {:context (fx/swap-context context assoc :status "Done!")})

(defmethod handler-fn ::processing [{:keys [fx/context config]}]
  (Thread/sleep 2000)
  {:dispatch {:event-type ::success-status}})

;;;;;;;;;;;;

(defn root [{:keys [fx/context]}]
  {:fx/type :v-box
   :children [{:fx/type :button
               :text "Option1"
               :on-action {:event-type ::entrypoint1}}
              {:fx/type :button
               :text "Option2"
               :on-action {:event-type ::entrypoint2}}
              {:fx/type :label
               :text (or (fx/sub-val context :status) "")}]})

Hi @remy, great question 🙂 The answer is don't block UI thread — you should perform your blocking computations in another thread and then dispatch new events from there, effects receive dispatch function as a second argument, you can use that. Example in the same e18: https://github.com/cljfx/cljfx/blob/master/examples/e18_pure_event_handling.clj#L28-L48

http-effect is an effect function, it receives dispatch! which is event dispatcher, and does asynchronous http requests, and then dispatches new events on response/error

That makes a lot of sense. Thanks again!