Hi Zoltan,
If you remove and re-add the shapefile you will of course loose the
virtual fields, as they are stored with the project and not with the data.
However, if you save a layer definition file along with the shapefile
and re-add that, they are preserved. So you can just store the layer
definition file along with the shape and you are fine to share the data
with your colleagues, preserving virtual fields ;-)
Andreas
On 07.11.2014 17:32, Zoltan Szecsei wrote:
Hi Andreas,
I'll fiddle with the Postgis idea - thanks.
The orange part below:
I closed the shapefile, deleted from legend and re-opened it - but
could not see my virtual field, nor the expression I used to create it.
Have I missed a trick somewhere?
Regards,
Z
On 2014/11/07 18:25, Andreas Neumann wrote:
Hi,
What you probably ask for are database triggers combined with
storage. This is not what virtual fields are for. If they were stored
- they wouldn't be called virtual ;-)
You can do that f.e. with Postgis. With shapefiles not. However, if
you share the project with the other PC, the virtual fields work fine.
Andreas
On 07.11.2014 17:21, Zoltan Szecsei wrote:
Hi Matthias,
Thanks for the quick answer.
The virtual field acts just like I want it to, except that it does
not permanently store the column in the attribute table.
I tried getting clever by then adding a second 'Field Calculation'
to update the existing 'Sheet' field from the virtual field, but
that won't do it either.
So, for me there are two shortcomings:
1. To be able to store and recall the 'Expression' and not lose it
after closing the Field Calculator
2. To be able to add the virtual fields that you create, into the
attribute table.
3. (And then of course to re-open the Shape file on another PC and
have these Field Calculations still functional)
Any further possibilities I can try?
Regards & thanks again,
Zoltan
On 2014/11/07 18:01, Matthias Kuhn wrote:
Hi Zoltan,
Since QGIS 2.6 this possibility exists. It is called "Virtual Field".
You must not create the attribute when creating the shapefile. Just open
the field calculator, create a new field in there and check the "virtual
field" checkbox.
Regards,
Matthias
On 07.11.2014 16:54, Zoltan Szecsei wrote:
Hi,
I'm using QGIS 2.6.0 on Win 7 x64 - installed via OSGEO4w
Is there a way to store your field calculator expression to always
process and update that specific field, should geometry be edited or
created for that Layer?
Let's say I want to create a blank POINT shape file, with a text
attribute called "Sheet".
Whenever a POINT is created or moved, I want this field to be
dynamically updated with:
tostring(abs(toint($y)))+tostring(abs(toint($x)))
For testing thus far have:
* created 2 points
* Opened the field calculator, clicked 'Update Existing Field' and
put in the expression.
* The two existing points now have the correct TEXT values in the
Sheet field
* I close the Field calculator
* Create a new point in my layer
* open the attribute table to find that the 'Sheet' field for this
new point is blank
* I open the Field Calculator and I cannot even find a way to call
back the previous expression I used.
Am I using the correct QGIS functionality to achieve what I need to,
and if so, where am I going wrong?
Thanks & regards,
Zoltan
--
===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services
P.O. Box 7, Muizenberg 7950, South Africa.
Mobile: +27-83-6004028
Fax: +27-86-6115323www.geograph.co.za
===========================================
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--
===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services
P.O. Box 7, Muizenberg 7950, South Africa.
Mobile: +27-83-6004028
Fax: +27-86-6115323www.geograph.co.za
===========================================
_______________________________________________
Qgis-developer mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
_______________________________________________
Qgis-developer mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
--
===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services
P.O. Box 7, Muizenberg 7950, South Africa.
Mobile: +27-83-6004028
Fax: +27-86-6115323www.geograph.co.za
===========================================
_______________________________________________
Qgis-developer mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
_______________________________________________
Qgis-developer mailing list
[email protected]
http://lists.osgeo.org/mailman/listinfo/qgis-developer
