Javascript to Clojurescript interop with react-spring

Question

I am trying to implement react-spring (https://www.react-spring.io/docs/hooks/basics) into my Clojurescript proct and I am struggling to translate this to clojurescript

import {useSpring, animated} from 'react-spring'
function App() {
  const props = useSpring({opacity: 1, 
                           from: {opacity: 0}})
  return <animated.div style={props}>I will fade in</animated.div>
}

So far this is what I have done: I have required the following:

(:require 
[useSpring]
[animated])

and in a let block I have something like so:

(defn example-app []
   (let [props (useSpring (->js {:opacity 1
                                 :from  {opacity: 0}}))]
    (def props props)
    [:animated.div {:style props} "I will fade in"]
))

The variable props returns this :

#js{:opacity #object[AnimatedValue [object Object]]}

Than this is how I render the animated object

(react-dom/render
(hx/f [example-app])
(goog.dom/getElement "example-app"))

This is the error that I get

#object[Error Invariant Violation: Objects are not valid as a React child (found: object with keys {ns, name, fqn, _hash, cljs$lang$protocol_mask$partition0$, cljs$lang$protocol_mask$partition1$}). If you meant to render a collection of children, use an array instead.
in core$example_app]

What am I doing wrong? What am I missing?

Answer 1

I did manage to get a basic example to work, hopefully it will help you get started:

• I cloned my example repo: https://github.com/dfuenzalida/cljs-react-intl/ (I created this for a test on react-intl, will work for you too)
• From the checked out repo, I installed react-spring with yarn install react-spring
• I edited the file shadow-cljs.edn to add the dependency on lilactown/hx:

{:source-paths ["src"]
 :dependencies [[lilactown/hx "0.5.3"]]
 :dev-http {8080 "target/"}
 :builds {:app {:output-dir "target/"
                :asset-path "."
                :target :browser
                :modules {:main {:init-fn app.main/main!}}
                :devtools {:after-load app.main/reload!}}}}

I replaced the contents of src/app/main.cljs with the react-spring example, adapted a bit:

(ns app.main
  (:require [hx.react :as hx :refer [defnc]]
            ["react-dom" :as react-dom]
            ["react-spring" :as spring]))

(defnc AppComponent [{:keys [title]}]
  (let [props (spring/useSpring (clj->js {:opacity 1 :from {:opacity 0}}))]
    [:<>
     [spring/animated.div {:style props} title]]))

;; App initialization

(defn mount-root []
  (react-dom/render
   (hx/f [AppComponent {:title "I will fade in"}])
   (js/document.getElementById "app")))

(defn main! []
  (mount-root)
  (println "[core]: loading"))

(defn reload! []
  (mount-root)
  (println "[core] reloaded"))

Finally, ran yarn install to download any missing deps and then yarn run html and yarn shadow-cljs watch app to start the compiler in watch mode. The console will show something like:

$ yarn shadow-cljs watch app
yarn run v1.17.3
$ /tmp/cljs-react-intl/node_modules/.bin/shadow-cljs watch app
shadow-cljs - config: /tmp/cljs-react-intl/shadow-cljs.edn  cli version: 2.8.74  node: v10.16.0
shadow-cljs - updating dependencies
...
shadow-cljs - dependencies updated
shadow-cljs - HTTP server available at http://localhost:8080
shadow-cljs - server version: 2.8.74 running at http://localhost:9630
shadow-cljs - nREPL server started on port 43685
shadow-cljs - watching build :app
[:app] Configuring build.
[:app] Compiling ...
[:app] Build completed. (156 files, 11 compiled, 0 warnings, 9.21s)

Once you load your app at http://localhost:8080, you should see something like:

The animation actually works, but I couldn't figure how to make the other examples to work (eg. the scroll example or the counter).

I hope this helps!