case class MetaData(
    id: Int,
    amount: Option[Int],
    currency: Option[Int]
)

object Main {
  def main(args: Array[String]): Unit = {
    val relevant = false
    val metadata = MetaData(1, Some(2), Some(3))
    val image = MetaData(4, Some(5), Some(6))

    val sourceMetaData: Boolean =
      metadata.amount.isDefined && metadata.currency.isDefined
    val sourceImage: Boolean =
      image.amount.isDefined && image.currency.isDefined

    val localAmount =
      if ((relevant && sourceMetaData) || !sourceImage) metadata.amount
      else image.amount

    val localCurrency =
      if ((relevant && sourceMetaData) || !sourceImage) metadata.currency
      else image.currency

    val metaData = MetaData(
      id = metadata.id,
      amount = localAmount,
      currency = localCurrency
    )

    print(metaData)
  }
}

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这是以可读格式编写此复杂场景的最佳可能方式。
如果有帮助的话，请接受。谢谢

听起来你需要稍微改变一下你的模型是如何建模的，这样金额和货币要么总是同时存在，要么两者都不存在。
类似于：

case class Amount(amount: Long, currency: String)

case class Metadata(id: Long, amount: Option[Amount])

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