reaction-example.clj

(defn greet-number
  "I say hello to an integer"
  [num]                             ;; an integer
  [:div (str "Hello #" num)])       ;; [:div "Hello #1"]

(defn more-button
  "I'm a button labelled 'More' which increments counter when clicked"
  [counter]                             ;; a ratom
  [:div  {:class "button-class"
         :on-click  #(swap! counter inc)}   ;; increment the int value in counter
         "More"])
       
(defn parent
  [] 
  (let [counter  (reagent.ratom/atom 1)]    ;; the render closes over this state
    (fn  parent-renderer 
      []
      [:div 
        [more-button counter]            ;; no @ on counter
        [greet-number @counter]])))      ;; notice the @. The prop is an int