[Qgis-developer] problem with feature request and updateFeature

[Nathan Woodrow]

I asked Jurgen to add the updateFeature a while ago in order to make the
API feel a bit cleaner. My issue was that you could update the attribute
values on the feature but you then still call changeFeatureAttribute for
each attribute which seems really crap.  I really only want to update the
feature and give it to the layer to handle calling the
changeFeatureAttribute calls with the id, index, value stuff.

- Nathan


On Tue, Apr 16, 2013 at 8:13 AM, Martin Dobias <wonder.sk at gmail.com> wrote:

> Going back to the older thread....
>
> On Sat, Mar 23, 2013 at 7:19 PM, Jürgen E. <jef at norbit.de> wrote:
> > On Sat, 23. Mar 2013 at 09:49:28 +1000, Nathan Woodrow wrote:
> >> Well the feature itself knows what values it started with. Every update
> in
> >> QgsFeature goes though the setAttribute, etc, call, you can just have an
> >> internal dictionary that logs when one of values is changed using those
> >> methods.
> >
> > Sure, you could do that.  But what for?  Just for updateFeature?  That
> method
> > is not even used anywhere.
> >
> > And one instance of QgsFeature is often used as buffer, so the tracking
> would
> > have to be reset at some point (setValid? setFeatureId?).
> >
> > IMHO one needs to be aware that currently multiple iterators are not
> working
> > for now.  Maybe Martin can comment on this - I guess he has plans
> continue to
> > work on this and the current state is for the time being.
>
> Maybe we should simply remove the updateFeature() function (or at
> least clearly document the side effect of issuing a request to the
> provider). Because of that request, even if the function worked in the
> nextFeature() loop, it would be highly inefficient to update features
> in such loop due to the many separate queries to the backend.
>
> Another reason for its removal would be that we do not use it anywhere
> in QGIS codebase and it's questionable to what extent it worked before
> the new vector API merge. For example, several providers used the same
> cursor for featureAtId() and nextFeature(), so the featureAtId() call
> during nextFeature() loop would re-create the cursor. Moreover,
> although OGR has a separate API calls for featureAtId(), OGR drivers
> that do not have efficient implementation of "get-feature-at-id" will
> simply fall back to internal "get-next-feature" loop, invalidating the
> reading state of nextFeature() loop.
>
> I have commented on multiple iterators in the other thread.
>
> Martin
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