Re: [Qgis-developer] how to create a new geometry from an existing one with python
Thanks I got it working now! I now have a different doubt, regarding geometry vertex iteration (sending another e-mail with it). On Sun, May 13, 2012 at 9:24 AM, Martin Dobias wrote: > Hi Ricardo > > On Sun, May 13, 2012 at 1:39 AM, Ricardo Filipe Soares Garcia da > wrote: >> [...] >> >> # python code >> >> line_geometry = >> qgis.utils.iface.mapCanvas().currentLayer().selectedFeatures()[-1].geometry() >> >> # approach 1 >> new_geometry = QgsGeometry(line_geometry) > > This approach is correct (and other seems to be fine, too). The > problem is elsewhere: you are being bitten by this bug: > http://hub.qgis.org/issues/777 > > Basically the problem is that the feature containing the line_geometry > gets deleted when the first line is executed. So your line_geometry > contains an invalid pointer leading to these strange errors. To > overcome this, store the list of features and then access it without > problems... > > Regards > Martin -- ___ ___ __ Ricardo Garcia Silva ___ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer
Re: [Qgis-developer] how to create a new geometry from an existing one with python
Hi Ricardo On Sun, May 13, 2012 at 1:39 AM, Ricardo Filipe Soares Garcia da wrote: > [...] > > # python code > > line_geometry = > qgis.utils.iface.mapCanvas().currentLayer().selectedFeatures()[-1].geometry() > > # approach 1 > new_geometry = QgsGeometry(line_geometry) This approach is correct (and other seems to be fine, too). The problem is elsewhere: you are being bitten by this bug: http://hub.qgis.org/issues/777 Basically the problem is that the feature containing the line_geometry gets deleted when the first line is executed. So your line_geometry contains an invalid pointer leading to these strange errors. To overcome this, store the list of features and then access it without problems... Regards Martin ___ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer
[Qgis-developer] how to create a new geometry from an existing one with python
Hi list I'm trying to code some tools for working with lines layers using python. One such tool is meant to create parallel lines. I am trying to create my new line geometry by first copying the geometry of a previously selected linestring and then translating it according to a specified distance. But I can't seem to find the correct way of copying the geometry. I am on Ubuntu 11.10, using QGIS compiled from master #033d58d, built today. For testing, I'm using layers created with the 'New Memory Layer' plugin, which uses the memory provider. I've tried the following approaches: # python code line_geometry = qgis.utils.iface.mapCanvas().currentLayer().selectedFeatures()[-1].geometry() # approach 1 new_geometry = QgsGeometry(line_geometry) -> Exception: unknown # approach 2 new_geometry = QgsGeometry.fromPolyline(line_geometry.asPolyline()) -> no error is thrown, but nothing happens # approach 3 wkb = line_geometry.asWkb() g.fromWkb(wkb, len(wkb)) -> RuntimeError: underlying C/C++ object has been deleted Thanks for your input! -- ___ ___ __ Ricardo Garcia Silva ___ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer
