Question

scala case class 这时候该怎么用

Answer 1

OK，让我们一劳永逸的解决这个问题吧，让大家见识一下Scala的强大：
给定一个字符串，自动转换为需要的case class

比如：

• 给定字符串"zhangsan,100,34"，定义了case class Person(name: String, id: Int, age: Int)，就能自动由字符串得到Person(zhangsan, 100, 34)
  

• 给定字符串"100,300,400"，定义了case class Vec(x: Int, y: Int, z: Int)，就能自动由字符串得到Vec(100, 300, 400)
  

• 首先给出最终的实现效果：


• @ case class Person(name: String, id: Int, age: Int)defined class Person@ Str2Class[Person]("ZhangSan,888,33").getres3: Person = Person("ZhangSan", 888, 33)@ case class Vec(x: Int, y: Int, z: Int)defined class Vec@ Str2Class[Vec]("100,200,300").getres5: Vec = Vec(100, 200, 300)



• 下面是具体的实现代码：


• object Str2Class {


•  import util.{ Failure, Success, Try }


•  trait Conveter[A] { def convert(text: String): Try[A] }


•  object Conveter {


•    def apply[A](implicit c: Conveter[A]): Conveter[A] = c


•    implicit object s2s extends Conveter[String] {


•      def convert(text: String) = Try(text)


•    }


•    implicit object s2i extends Conveter[Int] {


•      def convert(text: String) = Try(text.toInt)


•    }


•  }



•  import shapeless._


•  trait Parser[R <: HList] { def parse(xs: Seq[String]): Try[R] }


•  object Parser {    


•    def apply[R <: HList](implicit p: Parser[R]) = p


•    def fromFun[R <: HList](f: Seq[String] => Try[R]): Parser[R] = new Parser[R] {


•      def parse(xs: Seq[String]) = f(xs)


•    }


•    implicit object HNilParser extends Parser[HNil] {


•      def parse(xs: Seq[String]): Try[HNil] = xs match {


•        case Seq() => Success(HNil)


•        case _   => Failure(new RuntimeException("More items than expected."))


•      }


•    }


•    implicit def hListParser[A: Conveter, R <: HList : Parser]: Parser[A :: R] = fromFun {


•      case x +: rs => for(xv <- Conveter[A].convert(x);rv <- Parser[R].parse(rs)) yield xv::rv


•      case Seq() => Failure(new RuntimeException("Less items than expected."))


•    }


•  }



•  trait LineParser[A] {


•    def apply[R <: HList](text: String)


•                        (implicit gen: Generic.Aux[A, R], p: Parser[R]): Try[A] =


•      p.parse(text.split(",")) map (gen.from)


•  }


•  def apply[A] = new LineParser[A]{}}





==================原回答===================

Here we go:

• @ import shapeless._@ import syntax.std.traversable._@ import syntax.std.tuple._@ case class data(a: Int, b: Int, c: Int, d: Int, e: Int)defined class data@ type DATA = Int :: Int :: Int :: Int :: Int :: HNildefined type DATA@ val arr = "1\t2\t3\t4\t5".split('\t').map(_.toInt)arr: Array[Int] = Array(1, 2, 3, 4, 5)


•                                               @ val myData = data.tupled(arr.toHList[DATA].get.tupled)myData: data = data(1, 2, 3, 4, 5)