thanks @cfregly. I think I must need a lot more remedial learning on Scala.

The reference you provided works great, but when I try to translate it into my problem via:

val dfExploded = df.explode(df("price")) { case Row(pr: Array[Row]) => pr.map(pr => Price(pr(0).asInstanceOf[String], pr(1).asInstanceOf[String]) ) }

dfExploded.show()

I wind up with exceptions.