Arcadia Hello World.md

Arcadia's Hello World

1. Create a new, blank Unity 2D game, using Unity 5.4.0f3.

2. Unity menu: Edit -> Project Settings -> Player

   • Resolution & Presentation -> Run in Background* -> CHECK
   • Other Settings -> Api Compatibility Level -> .NET 2.0

3. Clone Arcadia Github into Assets directory and let Unity load it (be patient)

4. cd Assets/Arcadia/Infrastructure and run the ./repl program there, then

   • (require '[arcadia.core :refer :all])
   • Leave the REPL open for later

5. Drag a (random, small) image into your Unity Assets pane/window

6. Drag that image from the Assets window into the Scene pane/window, on top of the camera icon.

   • Confirm that the Hierarchy pane shows your image (it will be a Sprite now)

7. Rename that in the Hierarchy window to object-1

8. Create a new Clojure file in pathname Assets/minimal/core.clj with the contents below.

9. In the REPL, run this: (require '[minimal.core :refer :all]) to load it into the REPL

10. Now the magic happens: We're going to have the function first-callback get called every frame by linking (hooking) it to the object-1 object in the scene. This can only be done in the REPL for now, but the hook will show up in the Scene in the inspector. This will, for now, just spam the Unity Console window with boring messages.

11. We can access game objects by name using the Arcadia function objects-named. This returns a list. REPL: user=> (objects-named "object-1") -> (#unity/GameObject -22008)

12. Add the hook for the function in our minimal/core.clj file to the sprite we named object-1 in the REPL: user=> (hook+ (first (objects-named "object-1")) :update #'minimal.core/first-callback) -> #unity/GameObject -22008

13. Confirm this by clicking on object-1 in the Unity Hierarchy window and note in the Inspector that it says Update Hook (Script) with #'minimal.core/first-callback.

14. Make sure the Console window is showing. Click Play icon in Unity. Be patient. After a short time, your first Arcadia app will start running and the Console window will start showing a lot of messages like: Hello, Arcadia from UnityEngine.Debug:Log(Object).

15. Save your scene (whatever name you want). Quit Unity. Restart Unity and load your project. Hit Play. Everything should still work.

Assets/minimal/core.clj

(ns minimal.core
  (:use arcadia.core arcadia.linear))

(defn first-callback [o]
  (arcadia.core/log "Hello, Arcadia"))