Question

我有一个方法如下：

  protected def extract(implicit params:Params) =
    Map(
  "address" -> params.address,
  "city" -> reconcileCity,
  "region" -> params.region,
)collect {
    case (k, v) if v.isDefined => k -> v.get
  }

我想用另一种方法替换城市的价值如下：

  protected def reconcileCity(implicit params:Params)
  params.city match {
  case Some("madras") => "Chennai"
  case Some("bangalore") => "Bengaluru"
  case Some("gurgaon") => "Gurugram"
  case _ => params.city.mkString
}

但我得到的错误如下：

  Error:(177, 24) value isDefined is not a member of java.io.Serializable
  case (k, v) if v.isDefined => k -> v.get
  Error:(177, 44) value get is not a member of java.io.Serializable
  case (k, v) if v.isDefined => k -> v.get

请帮忙。

Answer 1

isDefined是Option类中存在的方法。但是你试图用String替换Option [String]，并在其上调用isDefined。

我假设params中的所有内容都是Option，因此您的代码应如下所示：

protected def reconcileCity(implicit params:Params)
params.city match {
case Some("madras") => Some("Chennai")
  case Some("bangalore") => Some("Bengaluru")
  case Some("gurgaon") => Some("Gurugram")
  case other => other
}

Answer 2

同意@ Alexey的回答isDefined和get是可以应用于Option类的方法。 Alexay建议将所有返回值更改为Some，但我建议仅将返回值更改为Some

  protected def extract(implicit params:Params) =
    Map(
      "address" -> params.address,
      "city" -> Some(reconcileCity),
      "region" -> params.region
    )collect {
      case (k, v) if v.isDefined => k -> v.get
    }


  protected def reconcileCity(implicit params:Params) = params.city.get match {
    case "madras" | "Madras" => "Chennai"
    case "bangalore" | "Banglore" => "Bengaluru"
    case "gurgaon" | "GurGaon" => "Gurugram"
    case _ => params.city.mkString
  }

在模式匹配匹配大小写之后动态添加元素到映射

2 个答案: