[QGIS-Developer] Geometry operations in Python

[Daan Goedkoop]

Yes, that works. Thank you!

2018-01-27 0:43 GMT+01:00 Nyall Dawson <nyall.dawson at gmail.com>:
> On 25 January 2018 at 17:30, Daan Goedkoop <dgoedkoop at gmx.net> wrote:
>> Thank you for the answers!
>>
>> Ok, so I don't need to manipulate the QgsMultiLineString directly. Yet
>> I cannot help to wonder a little bit about this (using a .shp file):
>>
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().asGeometryCollection()[0].asWkt()
>> 'LineString (4.83090675976269512 52.44278398333691626,
>> 4.89922802216601205 52.37283112413303598)'
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().asWkt()
>> 'MultiLineString ((4.83090675976269512 52.44278398333691626,
>> 4.89922802216601205 52.37283112413303598))'
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().asGeometryCollection()[0].asWkt()
>> 'LineString (4.83090675976269512 52.44278398333691626,
>> 4.89922802216601205 52.37283112413303598)'
>>>>> type(qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().constGet())
>> <class 'qgis._core.QgsMultiLineString'>
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().constGet().wkbType()
>> 5
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().constGet().numGeometries()
>> 0
>>>>> qgis.utils.iface.activeLayer().selectedFeatures()[0].geometry().constGet().asWkt()
>> <crash>
>>
>> Is this expected behaviour?
>
> I suspect what's happening here is that the feature is being garbage
> collected early, deleting the geometry and causing the unpredictable
> behavior - try this:
>
> f = qgis.utils.iface.activeLayer().selectedFeatures()[0]
> f.geometry().constGet()...... etc
>
>
>
> Nyall