On hindsight, I think my question is based on an incorrect assumption. In a
test case, whether you construct the data "on the fly" or map directly to
app-state the same number of "render" calls are made, so move on please,
nothing to see here :).
On Wednesday, 5 November 2014 13:38:46 UTC, Colin Yates wrote:
> Hi,
>
> Another question of idiomatic usage (will somebody *please* right a
> "JoyOfClojure" type book about om ;)).
>
> I have a hierarchy in my app-state (e.g. a hierarchy of locations). I also
> have app-state which stores the ids of the nodes that are selected
> {:reference {:locations {:id 1 :text "All locations" :children [...]}} :ui
> {:page-1 {:locations {:selected-ids []}}}}.
>
> However, for the purposes of this question let's assume I don't want to store
> the ids of the expanded nodes.
>
> My question is where to store this state:
>
> [tree local state in an expanded-ids []]
> If I do this (i.e. the tree's IInitState returns {:expanded-ids []}). Each
> component node in the tree is passed {:expanded? (id-in? (:id node)
> expanded-ids). Every time I expand or collapse the tree the tree component's
> top-level state (i.e. the expanded-ids vector) is changed which causes the
> whole tree to re-render.
>
> [tree local state in a projected-tree]
> In this scenario the component state is a hierarchy that merges the
> underlying (e.g. locations) tree with an "expanded?": {:id 1 :text "All
> locations" :children [...] :expanded? bool). As before, each tree node is now
> mapped to an individual node however, expanding or collapsing the tree only
> changes the data that a specific node is referencing so only that node needs
> to be re-rendered?
>
> [no local state]
> In this scenario there is no local state and it all comes from the app-state.
> This is actually a red herring as the question is the same - what data
> structure do you store?
>
> In both scenarios the same amount of dom manipulation is done due to om's
> optimisations and react's fantastic diff engine, but in the first the whole
> component is re-rendered, in the second only the individual node is
> re-rendered.
>
> It would seem that the second approach is the way to go, the more expensive
> the rendering the truer this is, except it has an additional complexity of
> wrangling together a bunch of data structures (as well as expanded there
> might be many more).
>
> Firstly, are my assumptions correct (they seem to be based on my initial
> investigations) and secondly, what do you all do?
>
> (Has anyone thought of writing a book on this stuff? I can't be the only
> person who has been doing this a while and been completely blown out of the
> water by the whole "treat the dom like a projection/state-machine/pure
> function" mind set?)
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