QgsExpression, the base for expression labels, is just not used for labels. It is also used for rules, actions, WFS filtering, attribute table filter.
I will consider it for string concatenation. - Nathan On Fri, Aug 2, 2013 at 8:28 AM, Bernd Vogelgesang <bernd.vogelges...@gmx.de>wrote: > mhm, > > Nathan, you wrote in the ticket: > "String + NULL = NULL. We don't treat NULL as empty string because it's > not correct to do so. NULL and empty mean two different things so are > treated differently." > > Sorry, but for "what" is that not correct? This might apply to database > actions etc. but forcing user to make somersaults with "coalesce" (what the > f... is that???) to prevent empty labels ... hey! It's just labeling! > > Making labeling a nerd-discipline is not fair ;) > > Just my 2 cents > Bernd > > Am 02.08.2013, 00:02 Uhr, schrieb Nathan Woodrow <madman...@gmail.com>: > > > Hey, >> >> QgsExpression doesn't treat NULL and Empty string as the same thing. Which >> is why we don't auto convert. To convert nulls in a field you should use >> the coalesce("Areatype",'') >> >> See http://hub.qgis.org/issues/**8369 <http://hub.qgis.org/issues/8369> >> >> - Nathan >> >> >> On Fri, Aug 2, 2013 at 7:35 AM, Larry Shaffer <lar...@dakotacarto.com >> >wrote: >> >> Hi Lene, >>> >>> On Thu, Aug 1, 2013 at 2:25 PM, Lene Fischer <l...@life.ku.dk> wrote: >>> >>> Hi Goyo >>>> The geometries is OK. >>>> I have a combined label Ex. >>>> Areatype || '\n' || $Area || ' m2' >>>> Now I found that if one field is empty (Even if there is NULL in the >>>> field), then the entire label will not be displayed. >>>> >>>> >>> When the expression-based label text was introduced, NULL values >>> supposedly where just converted to empty strings [0], i.e. if Areatype >>> was >>> NULL, one would expect at least 'm2' to be present in the label. >>> >>> Try enclosing your field name Areatype in double quotes. Also, try >>> without >>> the $Area function, but still with the || concatenation. If the label >>> still >>> does not contain any text, then it is probably a bug in how QgsExpression >>> handles NULL values from the data provider. If so, please create an issue >>> ticket [1]. Include a test project file, and try to list reproducible >>> steps, if you can. >>> >>> [0] >>> http://osgeo-org.1560.x6.**nabble.com/Expression-based-** >>> labeling-tp4100735p4100736.**html<http://osgeo-org.1560.x6.nabble.com/Expression-based-labeling-tp4100735p4100736.html> >>> [1] >>> http://hub.qgis.org/projects/**quantum-gis/issues<http://hub.qgis.org/projects/quantum-gis/issues> >>> >>> Regards, >>> >>> Larry >>> >>> >>> Regards >>>> Lene >>>> >>>> >>>> >>>> ______________________________**__________ >>>> Fra: Goyo [goyod...@gmail.com] >>>> Sendt: 1. august 2013 20:40 >>>> Til: Lene Fischer >>>> Cc: qgis-user@lists.osgeo.org >>>> Emne: Re: [Qgis-user] Label missing in Weekly >>>> >>>> 2013/8/1 Lene Fischer <l...@life.ku.dk>: >>>> > Hello >>>> > I´m using the new labelfunction - it is great!! - but som of the >>>> labels >>>> are >>>> > missing. I have a small project with only 9 polygons, but only 7 >>>> labels >>>> is >>>> > visible. >>>> > I´ve tried: >>>> > >>>> > Settings to "View all labels in all layers" >>>> > change attributefield and size >>>> > >>>> > Same result. Any suggestions? >>>> > Regards >>>> > Lene Fischer >>>> >>>> You might have invalid geometries. They are not labelled IIRC. >>>> >>>> Goyo >>>> >>>> >>>> ______________________________**_________________ >>>> Qgis-user mailing list >>>> Qgis-user@lists.osgeo.org >>>> http://lists.osgeo.org/**mailman/listinfo/qgis-user<http://lists.osgeo.org/mailman/listinfo/qgis-user> >>>> >>>> >>> >>> ______________________________**_________________ >>> Qgis-user mailing list >>> Qgis-user@lists.osgeo.org >>> http://lists.osgeo.org/**mailman/listinfo/qgis-user<http://lists.osgeo.org/mailman/listinfo/qgis-user> >>> >>> >>> > > -- > Bernd Vogelgesang * Siedlerstrasse 2 * 91083 Baiersdorf * +49-9133-825374 > > ______________________________**_________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/**mailman/listinfo/qgis-user<http://lists.osgeo.org/mailman/listinfo/qgis-user> >
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