It kinda was...
I have custom widgets on another tab of the form for letting the user
set up some things and I calculate values for attributes from that. So
it is not solvable with default values. Very good idea though, I wish it
would have been such an easy solution :))
When I posted also did not realise that it is not just about newly added
features but different for:
a) A newly added feature
b) A feature was added but not yet committed to the data source
c) An existing feature
In the end I solved it by looking at the feature ID differently:
```
feature_id = feature.id()
if feature_id == -9223372036854775808:
# this feature was newly added in this "form session"
edit_buffer = layer.editBuffer()
added_feats = edit_buffer.addedFeatures()
# get the id of the most recently added feature in the edit buffer
feature_id = min(list(added_feats.keys()))
# otherwise we are looking at an existing feature, committed or not
... # layer.changeAttributeValue(feature_id, ...)
```
This works fine even if multiple forms are opened at the same time and
OK is pressed on them in a random order.
I wonder if there is a named constant(?) or enum for that
-9223372036854775808 (-2**63) somewhere. It is used by any new feature
at that point in time.
https://github.com/qgis/QGIS/blob/a3413a9a9365fbd52ba6b0e2a6b9e55acc634cd4/tests/src/python/test_qgsvectorlayereditbuffer.py#L470
says "ID is NULL (-9223372036854775808)" but I bet there is a better way
in PyQt of saying "minimal INT64 value" instead of pasting the full
value into the code like I did?
Many thanks to Stefanos and Frank for their thoughts!
I had cross-posted to
https://gis.stackexchange.com/questions/474014/changing-attributes-of-a-newly-created-feature-in-python-form-init-code
and the user Matt gave me pointers into the right direction.
Feels super ugly and probably not the intended way to do this kind of
thing but WORKSFORME, done ;)
Cheers, Hannes
On 10.01.24 21:06, Stefanos Natsis via QGIS-Developer wrote:
Hi Hannes
This looks like an XY problem case!
If your actual goal is to:
> Any pointers on how to properly update a new feature's attribute
fields,
> that exist on a layer but are not shown the user with the QGIS' widgets
> in the attribute form?
then you simply need to set a Default Value for the field widget but
not add it to the drag and drop form designer. :)
If you really want to do this using form init code, you cannot do it
using the form's feature object as it is actually copied
by QgsAttributeForm before being saved to the layer.
You could connect to QgsAttributeForm::featureSaved() signal instead,
that emits the actual feature, but apparently the my_form_open
function is called twice: once when the form is loaded and once after
OK is clicked (bug??), so that would create the connection twice!
To avoid this you could connect to QgsAttributeForm::featureSaved()
only after OK is clicked!
Best
Stefanos
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