First of all, thanks for taking the time to reply.
Okay, maybe DatabaseCursor is the wrong name, DatabaseWrapper then.
When I use this
;; prevent cursor-ification
(extend-type d/DB
om/IToCursor
(-to-cursor
([this _] this)
([this _ _] this)))
it's preventing Om to turn d/DB into some kind of cursor. But when a change is
made to the database, Om re-renders the view. How does it figure that out?
When I pass my custom DatabaseWrapper, which implements IAssociative and
ILookup as well as om/IToCursor - it is not re-rendered anymore (I couldn't
extend d/DB directly, it caused DataScript internal issues). I also tried
implementing ICursor instead of IToCursor, but none of the methods were ever
called.
So how can I have a wrapper of a DataScript database that supports IAssociative
and still make Om re-render after any change to it? What's missing?
Stephan
On Sunday, January 25, 2015 at 3:29:33 PM UTC+1, David Nolen wrote:
> This won't be considered a cursor since it does not implement ICursor.
>
>
> David
>
>
> On Sun, Jan 25, 2015 at 5:09 AM, stephanos <[email protected]> wrote:
> Hey there,
>
>
>
> I'm trying to integrate Om and DataScript.
>
>
>
> At first I used David Nolen's gist [1] that implements 'om/IToCursor' for
> DataScript's DB type. That worked out well for some time. But now I try to
> apply Om's experimental support for writing all local state into the app
> state [2]. This requires an associative data structure because of its use of
> 'assoc' and 'get-in'.
>
>
>
> So I attempted to write a wrapper around the DataScript DB atom,
> DatabaseCursor. Now, while I succeeded in saving the local state to it by
> implementing IAssociative and ILookup, the app does not re-render on change
> anymore :(
>
>
>
> I originally assumed all I needed was to implement the IEquiv or IHash
> protocol, but that does not seem to work (both are never called). So I'm
> stuck right now. Here is my DatabaseCursor:
>
>
>
> (deftype DatabaseCursor [conn]
>
> ILookup
>
> (-lookup [this k]
>
> (-lookup this k nil))
>
> (-lookup [_ k not-found]
>
> (let [v (ffirst (d/q '[:find ?v :in $ ?k :where [?e :key ?k] [?e :value
> ?v]] @conn k))]
>
> (or v not-found)))
>
> IAssociative
>
> (-contains-key? [_ k]
>
> (not (empty? (d/q '[:find ?e :in $ ?k :where [?e :key ?k]] @conn k))))
>
> (-assoc [this k v]
>
> (let [old-id (ffirst (d/q '[:find ?e :in $ ?k :where [?e :key ?k]]
> @conn k))
>
> new-id (if old-id {:db/id old-id} {})]
>
> (d/transact! conn [(merge new-id {:key k, :value v})]))
>
> this)
>
> om/IToCursor
>
> (-to-cursor [this _] this)
>
> (-to-cursor [this _ _] this))
>
>
>
> How to I need to modify my custom cursor to make Om aware of changes to the
> DataScript DB?
>
>
>
> [1] https://gist.github.com/swannodette/11308901
>
> [2]
> https://github.com/swannodette/om/commit/ee9d92bf1191a391df804c066868c8180f9d64cf
>
>
>
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