CODEWITHSUNDEEP
scalacase-class
a.moussa
a.moussa

Reputation: 3297

how to use first attribute into second attribute from scala case class

I have created a case class like this:

case class MyClass[T](attName: String, getter: (ResultSet) => T)

I intantiate two exemple like this:

val ex1 = MyClass("name", (rs: ResultSet) => rs.getString("name"))
val ex2 = MyClass("age", (rs: ResultSet) => rs.getInt("age"))

I would like to avoid to use two time name and age for each line. Do you have any idea to reuse attName in the second attribute? Thank

Upvotes: 0

Views: 57

Answers (2)

Dima
Dima

Reputation: 40508

Something like this maybe:

class MyClass[T](name: String, getter: (ResultSet, String) => T) {
   def getIt(rs: ResultSet): T = getter(rs, name)
}

case object MyClassName extends MyClass[String]("name", _ getString _)
case object MyClassAge extends MyClass[Int]("age", _ getInt _)

Or just 

val ex1 = new MyClass("name", _ getString _)
val ex2 = new MyClass("age", _ getInt _)

Upvotes: 1

pedromss
pedromss

Reputation: 2453

Two choices:

Create an object to hold the static things like column names and use them as variables:

  object MyClass {
    object DbKeys {
      val name = "name"
      val age = "age"
    }
  }

  case class MyClass[T](attName: String, getter: (ResultSet) => T)

  val ex1 = MyClass(DbKeys.name, (rs: ResultSet) => rs.getString(DbKeys.name))
  val ex2 = MyClass(DbKeys.age, (rs: ResultSet) => rs.getInt(DbKeys.age))

Still with the object but this time with an abstract class and 2 case classes. Notice that when instanciating you don't specify column names.

  object MyClassArg {
    object DbKeys {
      val name = "name"
      val age = "age"
    }
  }

  abstract class MyClassArg[T](attName: String, getter: (ResultSet) => T)
  case class MyClassName() extends MyClassArg(DbKeys.name, (rs: ResultSet) => rs.getString(DbKeys.name))
  case class MyClassAge() extends MyClassArg(DbKeys.age, (rs: ResultSet) => rs.getString(DbKeys.age))

  val ex1 = MyClassName
  val ex2 = MyClassAge

I prefer the second choice because it makes for a cleaner use. You can make MyClassArg non abstract to allow more flexibility.

The getter can also be further abstracted to avoid repeating the rs.getString part.

Upvotes: 1

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