Combining multiple record field values into a new field

[Paul Riddle]

Hi All,

I am trying to find a way to build a better mouse trap.  My scenario is
this:
Schema:
{
  "name": "Sample Schema",
  "namespace": "nifi.examples",
  "type": "record",
  "fields": [
    { "name": "field1", "type": "string" },
    { "name": "field2", "type": "string" },
    { "name": "field3", "type": "string" }
    { "name": "combined", "type": "string" }
  ]
}

Say I have a CSV file:
field1,field2,field3
John,Mike,Lisa

I want to use an UpdateRecord to create a new field in each record called
"combined" with a value of "Mike Lisa" from field2 and field3

I am having difficulty finding a way to do that without using
PartitionRecord to add field values to attributes and then using expression
language to reference them in UpdateRecord to define the value of the
"/combined" field.

Is there a way to reference the field.value variable of another field in
UpdateRecord and cut out PartitionRecord in this scenario?

What I am looking for is something like ${field.value:field2()}
${field.value:field3()} if something like that exists.

Regards,
Paul