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live update virtual fields with children information #5274
Description
Discussed in #5272
Originally posted by rosaguilar May 27, 2024
Thanks a lot for this excellent app.
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 sums up to 100. In other words, use the field for constraint validation.
I created a virtual field, added it to the form, and used the expression below (suggested by @SeqLaz :
aggregate( layer:='child layer', aggregate:='sum', expression:="perc", filter:="uuid_parent" = attribute(@parent,'uuid') )The expression works well in an "actual" field in the table but not in a virtual field.
It would be nice to have this working in a virtual field because you don't have to add an unnecessary field to the database structure.
Activity
[-]Feature request: feature update in real time with a relation[/-][+]Feature request: feature update (virtual fields) in real time with a relation[/+][-]Feature request: feature update (virtual fields) in real time with a relation[/-][+]live update virtual fields with children information[/+]nirvn commentedon Oct 22, 2026
@rosaguilar , this PR will do what you want: #8143 -- you will however need to use the relation_aggregate function instead of the generic aggregate function (it's a newer/better function for what you are doing :) ).