You could simplify your fix code a small bit by using go-loop and when,
like this:
(go-loop []
(let [[v ch] (alts! [dump-chan (om/get-state owner :exit-chan)])]
(when (= ch dump-chan)
(.log js/console "dumping state:")
(.log js/console (pr-str (om/get-state owner)))
(recur))))
This won't work in your code because my-form's parent owns dump-chan, but
if a component owns the channel, an alternative approach is to simply close
dump-chan in IWillUnmount and change your go block to something like this:
(go-loop []
(when-let [v (<! dump-chan)]
(.log js/console "dumping state:")
(.log js/console (pr-str (om/get-state owner)))
(recur)))
In my own code, I've abstracted my go blocks into om-tools mixins that
handle the killing of go blocks.
I'm not sure why the second problem happens. As a general rule, I never
create new resources in render (IMO render should be pure functional: app
state and local state in -> new dom nodes out; but as the child stores the
channel between calls to parents render, this breaks that "rule") and I've
never had the issue.
Since base isn't being re-rendered in this case, I'm not sure why this
would be a problem here.
On 24 July 2014 02:35, Sean Corfield <s...@corfield.org> wrote:
> You'll want to read this thread:
> https://groups.google.com/forum/#!topic/clojurescript/DHJvcGey8Sc
>
> In particular:
>
> "So if you have code that's like this, those components will want to clean
> up after themselves in IWillUnmount."
>
> That should address your first problem?
>
> I'm not sure what to suggest right now about the second problem.
>
> Sean
>
>
> On Jul 23, 2014, at 4:19 PM, Alexander Hudek <alexan...@hudek.org> wrote:
>
> I've encountered two subtle but serious problems using om with core.async.
>
> The first one is illustrated by this code:
>
> https://github.com/akhudek/om-async-error
>
> First, one obvious solution here is to move the dump-chan inside the form
> state.
> However, it's written this way to illustrate the error which originally
> arose in a
> dialog component that took both an action channel that receives button
> presses
> and a dialog content component. It exposed the action channel in this way
> in
> order to be flexible.
>
> I believe the cause of this error is that when you toggle the form in the
> demo
> to off, it unmounts the component. However, the go-block is still active
> and
> listening to the channel. When you toggle the form back on, a new component
> is created and mounted. Now you have two components listening on the same
> channel!
>
> The ideal solution might be to find a way to end the go block when the
> component
> unmounts. This is easy to do on a case by case basis, but not easy to do
> in a
> completely generic fashion. Here is one solution:
>
>
> https://github.com/akhudek/om-async-error/blob/alts-fix/src/om_async_error/core.cljs
>
> The second problem is easy to fix, however, I don't understand why it
> happens.
>
> https://github.com/akhudek/om-async-error/tree/chan-opts-bug
>
> Instead of initializing the dump channel in the base components state, we
> initialize
> it when creating the form component. As soon as you start typing into the
> form
> the channel breaks. It was suggested on irc that this might be because of
> a
> re-render of base would create a new channel, but the form component will
> not
> be re-mounted because it's already mounted. However, putting in some debug
> code shows that there is no re-render of the base component occurring
> between
> when the channel works and when it doesn't.
>
> I'm posting this here mostly to warn people to be wary of these
> situations. Of
> course, if you have any suggestions or explanations for these I'd love to
> hear them.
>
> Alex
>
>
>
>
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