ClojureScript Protocol and Deftype View example

gistfile1.clj

(defprotocol View
  "View abstraction"
  (render [this some-param] "Renders view")
  (destroy [_] "Destroys view, runs cleanup"))

(deftype ProjectView [data]
  View
  (render [this some-param] [:h1 (str "Hello " (:name data) " some param we passed in " some-param)])
  (destroy [_] (println "Cleaning up")))

(def my-instance (ProjectView. {:name "Cuicca"}))

(render my-instance "yeah")
;; -> [:h1 "Hello Cuicca some param we passed in yeah"]
(destroy my-instance)
;; -> "Cleaning up"

;; Let's call render with something else than instance of View/ProjevtView:
(render {} "yeah")
;; -> Error: No protocol method View.render defined for type cljs.core/PersistentArrayMap: {}

;; Let's call render in another namespace:
(ns other)
(render {} "yeah")
;; -> TypeError: Cannot read property 'call' of undefined

;; Let's create an anonymous instance:
(defn create-anon-view [data]
  (reify View
    (render [this some-param] [:h1 (str "Hello " (:name data) " some param we passed in " some-param)])
    (destroy [_] (println "Cleaning up"))))

(def av (create-anon-view {:name "Cuiccis"}))

(render av "we are legion")
;; -> [:h1 "Hello Cuiccis some param we passed in we are legion"]

;; NOTE: render etc. needs to be :referred if we are using the view instance in another namespace