如何在scala中将赋值添加到空的dataframe现有列？

import org.apache.spark.sql.{SparkSession, Row}
import org.apache.spark.sql.types.{StructType, StructField, StringType}

val spark = SparkSession.builder().appName("Add value to empty DataFrame").getOrCreate()
val schema = StructType(Seq(StructField("column_name", StringType, nullable = true)))
val emptyDF = spark.createDataFrame(spark.sparkContext.emptyRDD[Row], schema)

val valueToAdd = "value"
val rowToAdd = Row(valueToAdd)

val updatedDF = emptyDF.union(spark.createDataFrame(Seq(rowToAdd), schema))