I am cobbling together my own little CLJS web framework and it is going
well but I am stumped by one bit of interop: supporting event handlers that
close over lexical variables. It seems to be a piece of cake for, inter
alia, Reagent. Here is an excerpt from the "simple" example, hacked a bit
(the "xxx" bits) to make sure I was seeing what I was seeing:
(defn color-input []
(let [xxx (atom 0)]
[:div.color-input
"Time color: "
[:input {:type "text"
:value @time-color
:on-change #(do (reset! xxx (rand-int 32767))
(println :xnow @xxx)
(reset! time-color (-> % .-target .-value)))}]]))
My approach is to convert the anonymous function to a string via STR and
specify it in the generate HTML as the handler. Just to see my html I have
a little test code:
(let [xxx (atom 42)]
(println :htm!!! (tag/to-html [(h1 {:onclick (on-evt #(swap! xxx inc))}
"Help!")])))
Here is `on-evt`:
(defn on-evt [cbfn]
(cl-format nil
"(~a)(event)"
(str cbfn)))
Here is what I see in the console:
:htm!!! <h1 onclick='(function (){return
cljs.core.swap_BANG_.call(null,xxx_12780,cljs.core.inc);})(event)'
id='0'>Help!</h1>
But JS understandably does not see the "xxx_12780".
I have tried more than once digging into the reagent code to see how it is
working its magic but always run into a dead end.
The one thing I do see when I inspect the DOM in the Chrome debugger is
that the handler is not there on the target element, just a react-id or
some such. This makes me think that the anonymous function itself (happily
compiled into JS closed over the lexical variable) is being stashed in a
dictionary under the react-id and that a handler at the document level is
navigating from the event target to the closure via the react-id.
That's just crazy enough to work. :) But am I just missing some simple CLJS
interop capability? Any other ideas?
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