Scala 使用键减少 Case class

Question

以下是我遇到的 2 个案例类的场景 -

case class Pack(name: String, age: Int, dob: String)

object Pack{
  def getPack(name:String, age: Int, dob:String): Pack = {
    Pack(name,age,dob)
  }
}

case class NewPack(name: String, pack: (List[Pack]))

object NewPack{
  def getNewPackList(data: List[Pack]): List[NewPack] = {
    val newData = for(x <- data )yield(x.name,List(x))
    val newPackData = for(x <- newData)yield(NewPack(x._1,x._2))
    newPackData
  }
}


val someData = List(Pack.getPack("x",12,"day1"), Pack.getPack("y",23,"day2"),Pack.getPack("x",34,"day3") )

val somePackData = NewPack.getNewPackList(someData)

someData和somePackData的值是这样的-

someData: List[Pack] = List(Pack(x,12,day1), Pack(y,23,day2), Pack(x,34,day3))

somePackData: List[NewPack] = List(NewPack(x,List(Pack(x,12,day1))), NewPack(y,List(Pack(y,23,day2))), NewPack(x,List(Pack(x,34,day3))))

现在我想得到下面提到的格式的最终数据。谁能建议我更好的方法。

finalData: List[NewPack] = List(NewPack(x,List(Pack(x,12,day1),Pack(x,34,day3)),NewPack(y,List(Pack(y,23,day2))))

Answer 1

这里稍微简化一下。

case class Pack(name: String, age: Int, dob: String)

case class NewPack(name: String, pack: List[Pack])

object NewPack{
  def getNewPackList(data: List[Pack]): List[NewPack] = 
    data.map{case pack@Pack(name, _, _) => NewPack(name, List(pack))}
}

请注意，通常情况下 class 不需要额外的工厂方法。如果您想稍后展示一些棘手的东西，您可以随时在伴随对象中定义自定义 apply。

此外，如果您打算按名称对包进行分组，您可以轻松地定义类似

的内容

def newPacksGrouped(data: List[Pack]): List[NewPack] =
  data.groupBy(_.name).map{case (name, packs) => NewPack(name, packs)}.toList

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