[Qgis-developer] Re: QGIS API: change layer field length

[romain riviere]

Hi Martin,

Thank you very much, this is exactly what i needed...
However, you were right...the truncation seems to be a limitation of the OGR
driver/Mapinfo Format.

Thanks again,

Romain,
*
*



2011/7/19 Martin Dobias <wonder.sk at gmail.com>

> Hi Romain
>
> On Sun, Jul 17, 2011 at 11:23 PM, romain <romain.riviere.974 at gmail.com>
> wrote:
> > Sorry, I think i haven't explained well what I want.
> >
> > I know how to get my fields' lengths from SpatiaLite.
> >
> > Here is what I've already done:
> > 1/ create QgsvectorLayer from spatiaLite table : vlayer
> > 2/ strore field's length in a python list: lengths
> >
> > One of my text fields (FIELD1) have 300 characters....
> >
> >
> > What my problem is when i want to save the layer as mapinfo file with :
> >
> > QgsVectorFileWritter.writteAsFromat(vlayer,........,mapinfo)
> >
> > -> The mapinfo File is created but all the fields are truncated at 254
> > char.... So, I lost informations on FIELD1...
>
> There is one more way how to use QgsVectorFileWriter:
> 1. construct QgsVectorFileWriter object
> 2. call addFeature() for each feature you want add
> 3. delete the writer object (in order to save changes)
>
> This is essentially what writeAsFormat() function does. But using the
> above approach has more flexibility: in the constructor you pass a map
> of fields - so instead of using input layer's field definitions you
> could change them and set higher (or lower) length, rename some fields
> etc.
>
>
> > I've tried to set fields lengths for my layer, in order to avoid
> truncature,
> > but, it doesn't change anything:
> >
> > fields=vlayer.dataProvider().fields()
> > for field in fields:
> >      fields[field].setLength(301)
>
> This will not work because you are changing the length only of the
> local object: this change will not get back to the provider.
>
>
> > The only thing I need is to pass an option to Qgsvectorfilewritter to
> change
> > fields maximum characters...
> > Does anybody know how to do this directly with OGR ? (within python, of
> > course)
>
> Another problem could be that the truncation is a limitation of the
> format or OGR driver...
>
> Regards
> Martin
>
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