scala - "using" function

Question

I've defined 'using' function as following:

def using[A, B <: {def close(): Unit}] (closeable: B) (f: B => A): A =
  try { f(closeable) } finally { closeable.close() }

I can use it like that:

using(new PrintWriter("sample.txt")){ out =>
  out.println("hellow world!")
}

now I'm curious how to define 'using' function to take any number of parameters, and be able to access them separately:

using(new BufferedReader(new FileReader("in.txt")), new PrintWriter("out.txt")){ (in, out) =>
  out.println(in.readLIne)
}

Answer 1

Starting Scala 2.13, the standard library provides a dedicated resource management utility: Using.

More specifically, the Using#Manager can be used when dealing with several resources.

In our case, we can manage different resources such as your PrintWriter or BufferedReader as they both implement AutoCloseable, in order to read and write from a file to another and, no matter what, close both the input and the output resource afterwards:

import scala.util.Using
import java.io.{PrintWriter, BufferedReader, FileReader}

Using.Manager { use =>

  val in  = use(new BufferedReader(new FileReader("input.txt")))
  val out = use(new PrintWriter("output.txt"))

  out.println(in.readLine)
}
// scala.util.Try[Unit] = Success(())