You have not implemented ICursor. Just implementing IToCursor is not enough.

On Sun, Jan 25, 2015 at 9:45 AM, stephanos <[email protected]> wrote:

> 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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