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Improve comments on handlers

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mike-thompson-day8 2015-03-02 07:57:11 +11:00
parent 9040937702
commit 6a3f2e4b74
1 changed files with 14 additions and 6 deletions
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20
src/re_frame/handlers.cljs
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@ -29,7 +29,7 @@
;; -- The Event Conveyor Belt -------------------------------------------------------------------- ;; -- The Event Conveyor Belt --------------------------------------------------------------------
;; ;;
;; Moves events from "dispatch" to the router loop. ;; Moves events from "dispatch" to the router loop.
;; This alows for aysnc handling of events. ;; Allows for the aysnc handling of events.
;; ;;
(def ^:private event-chan (chan)) ;; TODO: how big should we make the buffer? (def ^:private event-chan (chan)) ;; TODO: how big should we make the buffer?
@ -37,7 +37,14 @@
;; -- lookup and call ----------------------------------------------------------------------------- ;; -- lookup and call -----------------------------------------------------------------------------
(defn- handle (defn- handle
"Look up the handler for the given event, then call it, passing in 2 parameters." "Given an event vector, look up the right handler, then call it.
By default, handlers are not assumed to be pure. They are called with
two paramters:
- the `app-db` atom and
- the event vector
The handler is assumed to side-effect on the atom, the return value is ignored.
To write handlers that are pure functions, use the \"pure\" middleware at handler
registration time."
[event-v] [event-v]
(let [event-id (first-in-vector event-v) (let [event-id (first-in-vector event-v)
handler-fn (get @id->fn event-id)] handler-fn (get @id->fn event-id)]
@ -48,7 +55,7 @@
;; -- router loop --------------------------------------------------------------------------------- ;; -- router loop ---------------------------------------------------------------------------------
;; ;;
;; In a loop, read events from the dispatch channel, and route them ;; In a perpretual loop, read events from the dispatch channel, and route them
;; to the right handler. ;; to the right handler.
;; ;;
;; Because handlers occupy the CPU, before each event is handled, hand ;; Because handlers occupy the CPU, before each event is handled, hand
@ -57,7 +64,7 @@
;; In odd cases, we need to pause for an entire annimationFrame, to ensure that ;; In odd cases, we need to pause for an entire annimationFrame, to ensure that
;; the DOM is fully flushed, before then calling a handler known to hog the CPU ;; the DOM is fully flushed, before then calling a handler known to hog the CPU
;; for an extended period. In such a case, the event should be laballed with metadata ;; for an extended period. In such a case, the event should be laballed with metadata
;; Example usage: ;; Example usage (notice the ":flush-dom" metadata):
;; (dispatch ^:flush-dom [:event-id other params]) ;; (dispatch ^:flush-dom [:event-id other params])
;; ;;
;; router loop ;; router loop
@ -79,10 +86,11 @@
[event-v] [event-v]
(if (nil? event-v) (if (nil? event-v)
(warn "re-frame: \"dispatch\" is ignoring a nil event.") ;; nil would close the channel (warn "re-frame: \"dispatch\" is ignoring a nil event.") ;; nil would close the channel
(put! event-chan event-v))) (put! event-chan event-v))
nil) ;; Ensure nil return. See https://github.com/Day8/re-frame/wiki/Returning-False
;; TODO: remove sync handling. I don't like it, even for testing. ;; TODO: remove sync handling. I don't like it much, even for testing.
(defn dispatch-sync (defn dispatch-sync
"Invoke the event handler sycronously, avoiding the async-inducing use of core.async/chan" "Invoke the event handler sycronously, avoiding the async-inducing use of core.async/chan"
[event-v] [event-v]