[Qgis-developer] Field Calculator "permanence"

[Matthias Kuhn]

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:    +27-86-6115323     www.geograph.co.za
> ===========================================
>
>
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