[Qgis-developer] Improvements to the value relation widget: port to C++?

[Alessandro Pasotti]

2016-02-02 11:02 GMT+01:00 kimaidou <kimaidou at gmail.com>:

> Hi all,
>
> I also think merging things is the way to go, but we should keep the
> feature provided by the "value relation" widget : it is not used to add
> children referring the current object edited, but instead it is used to
> create a combo box containing labels helping to fill the field data which
> is a foreign key. For me, the logic is reversed. The data structure is the
> same, but the with a different point of view ( child or parent).
>
> Regards,
> Michaël
>


Hi,

I don't see such a difference: the main difference with the current
implementation of value relation widget is that the (optional) filtering of
the items in the combo is dynamic: every time a value changes in the other
fields of the form, the values in the related combo are filtered again
against the expression, that in turn has access to the current values of
the other fields.

This means that the cache for the values in the combo is built against
unfiltered values (and can be optionally disabled).

If you don't set an expression that uses the new function to access to the
other fields in the form, this widget behaves exactly as the current value
relation widget.


-- 
Alessandro Pasotti
w3:   www.itopen.it
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