On Sunday, March 29, 2015 at 11:38:44 PM UTC+11, Colin Yates wrote:
> Hi all, I have read the docs but might have overlooked something.
>
> I keep seeing components being updated in response to state changes but I
> don't see the latest state in that component.
>
> For example, in the following:
>
> (defn- make-rows
> [on-click selected-id]
> (js/console.log "rows has selected-id: " selected-id)
> [:tbody
> (for [idx (range 10)]
> [:tr
> {:class (when (= selected-id idx) "selected")
> :on-click #(do (on-click idx) nil)}
> [:td "Some state"]])])
>
> (defn make-table []
> (let [selected-id (subscribe [:search/selected-journey-id])]
> (fn []
> (js/console.log "make-table has selected-id: " @selected-id)
> [table/table {:headers [{:class :ignore-me :text "whatever"}]
> :rows (make-rows #(dispatch [:search/select-journey-id
> %])
> @selected-id)}])))
>
> when I call [make-table] then I can see both make-table and make-rows being
> called with the new selected-id, but table/table never gets the new
> selected-id, it is always called with the old selected-id. It is as if the
> invocation to (rows) is cached.
>
> Changing make-table to use [make-rows] makes the problem worse as only
> make-tables is called in response to the selected-id changing.
>
> The only way I can get this to work is to make-rows itself subscribe to the
> selected-id:
>
> (defn- make-rows
> [on-click]
> (let [selected-id (subscribe [:search/selected-journey-id])]
> (fn []
> (js/console.log "rows has selected-id: " @selected-id)
> [:tbody
> (for [idx (range 10)]
> [:tr
> {:class (when (= @selected-id idx) "selected")
> :on-click #(do (on-click idx) nil)}
> [:td "Some state"]])])))
>
> (defn make-table []
> [table/table {:headers [{:class :ignore-me :text "whatever"}]
> :rows [make-rows #(dispatch [:search/select-journey-id
> %])]}])
>
> Can somebody please explain why calling an fn with a @subscription is the
> wrong thing to do.
>
> Thanks for reading this far ;).
Colin, any chance you can create a pared-back repo showing the issue? My guess
is that you can make it very simple by removing all use of re-frame and just
using ratoms in place of subscriptions.
So instead of something like:
[blah (subscribe [:something])]
you can simulate via:
[blah (reagent/atom (some data))]
Then you can reset! blah to simulate subscription changes.
After all, a subscription just returns something which behaves much like a
ratom.
--
Mike
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