TonyFMCMC
commented
4 years ago So, I think there is a timing issue here, and now that I think about it it is obvious. The expression is only evaluated when the polygon is created and the associated form loaded, or on save (depending on whether "Capture and save", "Capture only" or "Save only" is selected in Roam Config Manager.
So instead I created an event on the 'Activity' field, on update, setvalue, Details, only when True, New value concat( attribute( get_feature( 'Activities','ActivityID',@value),'Description'),' ',"Details").
And this worked! Notes for the curious in the new value expression:
- Fields from the form need double quotes, and use the name of the field the widget is based on, not the name as it appears on the form or in the 'name' field on the form designer.
- use @value for the value as changed of the field the event is based on.
- use single quotes on other items inside the attribute and get_feature functions.
- I concatenated with the current value of the Details field so that if information had already been manually entered it would not be lost. The downside is that if someone changes their mind about the Activity, the Details field accumulates changes. Ideally if manual changes had been entered in the Details field, a new Description would not be added, but how do I discriminate between manually entered text and text automatically added by a previous event?
A bit more documentation of this functionality would be helpful please.
What is the correct expression format to populate a field using the 'Capture value from field' option in Roam Config Manager where the capture layer is non-geographic.
E.g a field on my form is "Activity". I want to populate another field on the form "Details" with the value in a local geopackage layer "Activities" in a column "Description", where the column "ActivityID" equals the entry on the field on my form "Activity".
So I select Activities as the capture layer, select Description as the Value Field, but I think the problem is in the join expression. Naively I would expect that "ActivityID"="Activity" would work. But it doesn't, nor does the reverse. Nor attribute("Activities","ActivityID")="Activity", nor anything else I tried.
Help please. Roam 2.6.0, QGIS 2.18