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Accepted
Oleg
Asked:2020-12-06 15:52:19 +0000 UTC2020-12-06 15:52:19 +0000 UTC

具有动态键的 Scala Map

  • 772

同事，是否可以根据您的条件（值的存在）动态创建带有键的映射？

例如对于一个对象Person：

case class Person(name: String, surname: String, age: Int)

用键做地图，但不是全部，而是根据一定的条件。就像是：

val p1 = Person("Вася", "", "35")
Map(
  if (p1.name.nonEmpty()) "name" -> p1.name,
  if (p1.surname.nonEmpty()) "surname" -> p1.surname,
  "age" -> p1.age.toString 
)

因此，对于 object p1，您应该得到一个不是三个，而是两个键的映射：

Map("name" -> "Вася", "age" -> "35")

姓氏键丢失

map

1 个回答

  1. Best Answer

    像这样？

    case class Person(name: String, surname: String, age: Int)

val p1 = Person("Вася", "", 35)

def person2MapVer1(p: Person): Map[String, String] = {
  var map = Map.empty[String, String]

  if (p.name.nonEmpty) map += "name" -> p.name

  if (p.surname.nonEmpty) map += "surname" -> p.surname

  map += "age" -> p.age.toString

  map
}


def person2MapVer2(p: Person): Map[String, String] = {
  val validateName: Person => Option[(String, String)] =
    p => if (p.name.nonEmpty) Some("name" -> p.name) else None

  val validateSurname: Person => Option[(String, String)] =
    p => if (p.surname.nonEmpty) Some("surname" -> p.surname) else None

  val validateAge: Person => Option[(String, String)] =
    p => Some("age" -> p.age.toString)

  val validations: List[Person => Option[(String, String)]] =
    List(validateName, validateSurname, validateAge)

  validations.foldLeft(Map.empty[String, String]) {
    case (acc, validation) => acc ++ validation(p)
  }
}

person2MapVer1(p1)
person2MapVer2(p1)
    • 2

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