scala 2.10中的泛型类型解析器

Question

我正在使用Scala 2.10编写通用值解析器.输入是一个字符串,输出是泛型类型,由用户给出.

我唯一能想到的是

val StringTYPE = classOf[java.lang.String]

def parseValue[T: ClassTag](str: String): T = {
  implicitly[ClassTag[T]].runtimeClass match {
    case java.lang.Integer.TYPE => str.toInt.asInstanceOf[T]
    case java.lang.Long.TYPE => str.toLong.asInstanceOf[T]
    case StringTYPE => str.asInstanceOf[T]
    case _ => throw new Exception("Unknown type")
  }
}

但它看起来非常冗长和复杂,所以我想知道有没有更简单的方法来做到这一点？

Answer 1

在编译时条件中使用运行时错误似乎很奇怪.你考虑过类型课吗？

trait Readable[T] {
  def read(str: String): T
}

object Readable {


  implicit object IntIsReadable extends Readable[Int] {
    def read(str: String): Int = str.toInt
  }

  // ... provide similar objects for any types that can be "read" ...
  // if possible, inside object Readable 
  // or inside the companion object of the type you want to make readable. 
  // Otherwise, ensure that the implicit is in scope when calling Read
}


def readValue[T: Readable](str: String): T = implicitly[Readable[T]].read(str)