om.core/update-state! about om

[gdeer81]

Did you have something like this in mind?

first we define a function that applies a state transition function to the state

(defn apply-trans-fun
  "Applies the transition function to the state and returns the updated state"
  [state trans-fun]
  (trans-fun state))

then we reduce the state with our application function

(defn update-state!
  "Updates the state by applying all transition functions in order."
  [state trans-funs]
  (reduce apply-trans-fun state trans-funs))

This isn't analogous to set-state! so I'll study the set-state! function to see if I can come up with something better

[swannodette]

om.core/update-state! is really more about being idiomatic. It's more idiomatic to take some state and do some functional operations on it and return a value over banging on it several times in succession. I was thinking about something more analogous to cljs.core/update-in

[pbostrom]

Would swap! be a better analogy? Something like

(defn swap-state!
  "Takes a pure owning component and sets the state of the component to be:
   (apply f current-state args)."
  ([owner f]
    (allow-reads
      (let [props  (.-props owner)
            state  (.-state owner)
            cursor (aget props "__om_cursor")
            path   (-path cursor)
            pstate (or (aget state "__om_pending_state")
                       (aget state "__om_state"))]
        (aset state "__om_pending_state" (f pstate))
        ;; invalidate path to component
        (if (empty? path)
          (swap! (-state cursor) clone)
          (swap! (-state cursor) update-in path clone)))))
  ([owner f x]
    (swap-state! owner #(f % x)))
  ([owner f x y]
    (swap-state! owner #(f % x y)))
  ([owner f x y & args]
    (swap-state! owner #(apply f % x y args))))

;; Usage: 
(om/swap-state! owner assoc :foo 1 :bar 2)

I tested this out, it seems to work pretty well. I suppose we might want to enforce an invariant that the new state is always a map. I'm open to any other suggestions.

[swannodette]

fixed 4405497