How to implement feature update in real time with a relation

[rosaguilar]

I am looking for functionality in Qfield like the one described at
feature-live-update
I have defined some relations in my Qgis project and they are working well.
I need to sum all the "children" and validate that a certain attribute sum up to 100.
I created a virtual field, added it to the form, and used the expression below:

relation_aggregate(
  'obs_child_6_obs_point_id_obs_point__point_id', 
  'sum',
  "perc"
)

"perc" is an attribute of the "children".
This works well in QGIS but not in Qfield.
Any workaround? suggestions>?

[SeqLaz]

Hello @rosaguilar,

It's best to avoid a virtual field and use an actual field instead. Could you try the expression below for real-time calculations? Also, ensure that you have the "Apply default value on update" activated:

aggregate( layer:='child layer', aggregate:='sum', expression:="perc", filter:="uuid_parent" = attribute(@parent,'uuid') )

If you could provide a sample of the project, it would help better.

[rosaguilar]

Hi, @SeqLaz
Thanks a lot. It works with an actual field. The key is that the value does not get automatically updated after each child insertion. When another field in the parent form is edited, then the value is computed. Foe now, that is good for me. Thanks.