On Monday, November 3, 2014 3:53:45 AM UTC-6, Colin Yates wrote:
> The performance problem was due to me incorrectly mutating the data to the
> component. Rather than:
>
> (om/build-all child-component (map (fn [child] (assoc child :selected? (=
> (:id child) selected-id) :selected-row-fn (fn [p] (om/set-state! owner
> :selected-id (:id p).....)) child-data)
>
> I now do:
>
> (om/build-the-component data
> {:fn (fn [p] (assoc data :selected? (= (:id child) ...))
> :opts {:selected-row-fn (fn [p] (om/set-state! owner :selected-id (:id
> @p)))}})
>
> In other words, the lesson I am learning is that the cursor really wants to
> be domain orientated and change as little as often.
>
> Am I right in thinking that for component instance specific immutable data
> (e.g is it selected), use :fn. For component class level data use :opts (e.g.
> selected callbacks). For global data there is always access to (om/root
> {:shared...}) but that isn't applicable in this case?
>
> Thanks.
>
> On Sunday, 2 November 2014 23:29:19 UTC, Mike Haney wrote:
> > Sounds like a IE8 issue. I've never seen anything like that low
> > performance, even on mobile. Are you using any polyfills or shims?
> >
> > Check out the section "Browser Support and Polyfills" here:
> > http://facebook.github.io/react/docs/working-with-the-browser.html
a child component, when receiving data ("props") from a parent component, will
compare the data to the data it previously received. if the data has changed,
the child component will re-render. the props it receives will always have
been passed through the function in :fn (provided to om/build or om/build-all
in the parent component). so any transformations in that function will always
participate in the child component's determination to re-render (or not). for
example, if your function in :fn assoc's a new unique id to the props every
time it is called, the child component will re-render every time it receives
props.
anything the child component receives in :opts is not evaluated for the
re-render-or-not decision. if you put values in :opts, and those values have
changed but the props have not, the child component will not re-render.
because of this distinction in how child components process the two, it
generally makes sense to put a callback function in :opts, and a transforming
function in :fn.
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