Assign field value to attribute in ABAP ST transformation?

I'm using SAP Simple Transformation and I want to set value of unitCode attribute from ABAP field which is defined inside my structure. Let's say it's UNITCODE field.

 <cbc:InvoicedQuantity tt:value-ref="INVOICEDQUANTITY" unitCode="C62" unitCodeListID="UNECRec20"/>

Right now unitCode is hardcoded as value C62 but I want that this attribute takes value from ABAP UNITCODE field (in same structure as INVOICEDQUANTITY). How can I make this happen?

Thanks in advance!

Solution

You may initialize an attribute from an ABAP variable using tt:attribute:

  <cbc:InvoicedQuantity tt:value-ref="INVOICEDQUANTITY" unitCodeListID="UNECRec20">
    <tt:attribute name="unitCode" value-ref="UNITCODE"/>
  </cbc:InvoicedQuantity>

Below is a Minimal Reproducible Example:

ABAP :

DATA : BEGIN OF ls_data,
         invoicedquantity TYPE decfloat34,
         unitcode         TYPE string,
       END OF ls_data.
ls_data = VALUE #( invoicedquantity = 1000 unitcode = 'C62' ).
CALL TRANSFORMATION ztransfo
    SOURCE abaproot = ls_data
    RESULT XML DATA(xml).

Simple Transformation ZTRANSFO:

<?sap.transform simple?>
<tt:transform xmlns:tt="http://www.sap.com/transformation-templates"
      xmlns:ddic="http://www.sap.com/abapxml/types/dictionary">
  <tt:root name="ABAPROOT"/>
  <tt:template>
  <ROOT xmlns:cbc="http://xxx" tt:ref="ABAPROOT">
    <cbc:InvoicedQuantity unitCodeListID="UNECRec20">
      <tt:attribute name="unitCode" value-ref="UNITCODE"/>
      <tt:value ref="INVOICEDQUANTITY"/>
    </cbc:InvoicedQuantity>
  </ROOT>
  </tt:template>
</tt:transform>

Expected XML result:

<?xml version="1.0" encoding="UTF-8"?>
<ROOT xmlns:cbc="http://xxx">
  <cbc:InvoicedQuantity unitCodeListID="UNECRec20" unitCode="C62">
    1000
  </cbc:InvoicedQuantity>
</ROOT>