嵌套Options Monad上的FlatMap或For-comprehension

Question

有没有人能帮我把这个转换成flatMap或者for- Can？我知道如何处理嵌套选项的更多微不足道的场景。

    case class Person(name: String, signficantOther: Option[String])
    val nightclubPeoples : Option[Seq[Person]] = ???

    def significantOthers(nightClubPeoples : Option[Seq[Person]]) : List[String] = {
      nightclubPeoples match {
        case Some(x) => x map { y : Person => 
          y.significantOther match {
            case Some(z) => z
            case None => "No Signficant Other"
          }
        }.toList
        case None => Nil
      }
    }

Answer 1

我想我会用一个折叠键：

nightclubPeoples.fold[List[String]](Nil)(_.flatMap(_.signficantOther)(collection.breakOut))

Answer 2

Sascha Kolberg的答案是，正如我所认为的，对于你的问题，一个更好的解决方案(只是省略了signficantOther为空的情况，即"No Signficant Other“不会出现在结果列表中)，然而，因为你要求”将其转换为flatMap或用于理解“，所以代码如下所示。

case class Person(name: String, signficantOther: Option[String])
val nightClubPeopleOpt : Option[Seq[Person]] = Some(Person("name", Some("1")) :: Person("name1", None) :: Nil)

def significantOthers(nightClubPeopleOpt : Option[Seq[Person]]) = {
    for {
        nightClubPeople <- nightClubPeopleOpt
    } yield {
        // scenario 1
        // if signficantOther is empty, then it should be ignored
        // Answer -> List(1)
        nightClubPeople.flatMap(_.signficantOther).toList

        // scenario 2
        // if signficantOther is empty, then we use the default "No Signficant Other"
        // Answer -> List(1, No Signficant Other)
        nightClubPeople.map { nightClubPerson =>
            nightClubPerson.signficantOther.getOrElse("No Signficant Other")
        }.toList
    }
}.getOrElse(Nil)


println(significantOthers(nightClubPeopleOpt))

Answer 3

这就是了：

nightclubPeoples.toSeq.flatMap(_.map(_.signficantOther.getOrElse("No Signficant Other")))