Read a tuple from a file in Scala-CodePudding

my Task is to read registrations from a file given like:

Keri,345246,2
Ingar,488058,2
Almeta,422016,1

and insert them into a list(Tuple of (String, Int, Int).

So far I wrote this:

The problem is that I don‘t understand why I can't try to cast value2 and value3 to Int even tho they should be Strings because they come from an Array of Strings. Could someone tell me, what my mistake is, I am relatively new to Scala

CodePudding user response：

In Scala, in order to convert a String to an Int you need explicit casting.

This can be achieved like this if you are sure the string can be parsed into a integer:

val values = values(1).toInt

If you cannot trust the input (and you probably should not), you can use .toIntOption which will give you a Option[Int] defined if the value was converted successfully or undefined if the string did not represent an integer.

CodePudding user response：

What is the point of using Scala if you are going to write Java code?

This is how you would properly read a file as a List of case classes.

import scala.io.Source
import scala.util.Using

// Use proper names for the fields.
final case class Registration(field1: String, field2: Int, field3: Int)

// You may change the error handling logic.
def readRegistrationsFromFile(fileName: String): List[Registration] =
  Using(Source.fromFile(fileName)) { source =>
    source.getLines().map(line => line.split(',').toList).flatMap {
      case field1Raw :: field2Raw :: field3Raw :: Nil =>
        for {
          field2 <- field2Raw.toIntOption
          field3 <- field3Raw.toIntOption
        } yield Registration(field1 = field1Raw.trim, field2, field3)

      case _ =>
        None
    }.toList
  }.getOrElse(default = List.empty)

(feel free to ask any question you may have about this code)