Scala – how to print case classes like (pretty printed) tree

Check out a small extensions library named sext. It exports these two functions exactly for purposes like that.

Here’s how it can be used for your example:

object Demo extends App {

  import sext._

  case class ClassDecl( kind : Kind, list : List[ VarDecl ] )
  sealed trait Kind
  case object Complex extends Kind
  case class VarDecl( a : Int, b : String )


  val data = ClassDecl(Complex,List(VarDecl(1, "abcd"), VarDecl(2, "efgh")))
  println("treeString output:\n")
  println(data.treeString)
  println()
  println("valueTreeString output:\n")
  println(data.valueTreeString)

}

Following is the output of this program:

treeString output:

ClassDecl:
- Complex
- List:
| - VarDecl:
| | - 1
| | - abcd
| - VarDecl:
| | - 2
| | - efgh

valueTreeString output:

- kind:
- list:
| - - a:
| | | 1
| | - b:
| | | abcd
| - - a:
| | | 2
| | - b:
| | | efgh