FormTemplate ExpressionInfos not working

[JanHellenberg]

I am using FormTemplate in a FeatureForm to show elements from a Featurelayer, which works fine. But when I try to replace the field with a calculated expression using the FormTemplates ExpressionInfos, nothing happens and the value from the Featurelayer field is still showing. I have tried with 4.27 and 4.28 and I get no errors in console.

const featureForm = new FeatureForm({

view: view,

layer: MyLayer,

feature: view.popup.selectedFeature,

formTemplate: {

expressionInfos: [

  { 

  name: 'Test',

  title: 'Test', 

  expression: '$feature.Field2',

  returnType: 'string',

  },],

elements: [

  new FieldElement({

  type: 'field',

  fieldName: 'Field1',

  label: 'Label: ',

  valueExpression: 'Test',

}),],},})

So, in this simplified example I would like to display the Field2 value (as calculated in the expression) instead of Field1 but Field1 is still displayed. Of course, my plan is to perform a more complex expression once I get this to work. Can someone help?

[ThomasHarner1]

Hi Jan, 

From what I understand it appears that a Field Element in a Form is pretty strict about the schema/rules of the underlying table/servcie endpoint, and cannot return a value from an ExpressionInfo unless that targeted field is set to not be editable.

Try and add the line "editableExpression: 'return false'" below the valueExpression parameter and see if the value shows up then. I think the idea with valueExpressions is that they dynamically calculate other fields based on another and are not intended to be directly modified by a user. 

Thomas