[Development] RFC: unified data model API in QtCore => thin wrapper proposal

[Jason H]

+1 this.

I'd prefer Arne's over the bind below. I do want value updates to be emitted so that we only have to change the data to keep dependent structures updated. I've suggested having some kind of xpath watcher facility... 

Having done some web UIs powered by a Ajax, (and qt will undoubtedly power some web backends) you need a facility to keep 2 trees in sync - the server data and the web UI model.  However it should be the same for QML or widget UIs... And in my dream world, a proper QML web UI. But no matter how it works, you need to be able to broadcast minimal data changes to the tree to listeners (clients).




> Sent: Friday, June 15, 2018 at 3:46 PM
> From: "Tor Arne Vestbø" <Tor.arne.Vestbo at qt.io>
> To: "Arnaud Clère" <arnaud.clere at minmaxmedical.com>
> Cc: "Thiago Macieira" <thiago.macieira at intel.com>, "development at qt-project.org" <development at qt-project.org>
> Subject: Re: [Development] RFC: unified data model API in QtCore => thin wrapper proposal
>
> 
> 
> > On 15 Jun 2018, at 13:31, Arnaud Clère <arnaud.clere at minmaxmedical.com> wrote:
> > 
> [snip]
> 
> > Most user-defined bind methods would be very simple and the type system would 
> > guarantee that data is well-formed (no sequence or record left open...):
> > 
> >    struct Person {
> >        QString m_firstName, m_lastName;
> >        int m_age;
> > 
> >        template<TResult>
> >        TResult bind(Val<TResult> value) { return value
> >            .record()
> >                .sequence("name")
> >                    .bind(m_firstName)
> >                    .bind(m_lastName)
> >                .out()
> >                .bind("age" , m_age); // automagically closes opened record
> >        }
> >    };
> 
> Not commenting on this API, but I’d like to note that the API I brought up as “missing” from my use-case was a more “light weight” in-place edit API, where the user does not have to define bindings to data structures like above. Similar to e.g. python:
> 
> >>> data = json.loads('{ "foo": [1, 2, 3] }')
> >>> data
> {u'foo': [1, 2, 3]}
> >>> data["foo"][0] = 42
> >>> data
> {u'foo': [42, 2, 3]}
> 
> With our existing APIs I’d expect:
> 
> QJsonDocument doc;
> doc[“foo”][0] = 42;
> 
> Tor Arne 
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