Alright, so here's a rule that worked for me as an attribute rule. In your case given the context, what you might do is instead of using the $datastore of FeatureSetByName, you might choose $map. Otherwise, you could use FeatureSetByPortalItem, which would allow you to access the layer even if it isn't in the map.
Essentially, in Field Maps form designer, you would add this as a Calculated Expression, making that field uneditable for the user. You might need to tweak this because Arcade profiled are different across applications, but this should get you a good chunk of the way there. Just adjust your layer names, feature names etc as necessary.
// This is the polygon feature
var nrAreas = FeatureSetbyName($datastore,'NR_Management')
// intersect the polygons
var interArea = first(intersects($feature,nrAreas))
// This is the relted table
var matchTable = FeatureSetbyName($datastore,'NR_Management_Form')
// if there's no intersecting area, end the expression
if (interArea == null){return}
// get the global ID of the polygon
var interAreaGlobal = interArea.GlobalID
// Filter polygons based on shared ID. In this case, NRArea_Rel is a GUID type
var filterStatement = 'NRArea_Rel = @interAreaGlobal'
// Filter all the related forms
var relatedForms = Filter(matchTable,filterStatement)
// Get the data from the most recent form, determined by the 'Date' Field
var recentForm = first(OrderBy(relatedForms, 'Date ASC'))
// Identify the maintenance performed
var maint = recentForm.MaintPerformed
// Write the above value into the attribute this rule runs on
return maint
Happy mapping,
- Zach
