Using the using package

using.scala

import java.io.BufferedReader
import java.io.ByteArrayInputStream
import java.io.InputStreamReader

import utils.using._

object Main extends App {
  // the "used" instance is passed to the body i.e. "in" is of type BufferedReader
  using(new BufferedReader(new InputStreamReader(new ByteArrayInputStream("Testing using".getBytes)))) { in =>
    println(in.readLine)
  }

  val i1 = new BufferedReader(new InputStreamReader(new ByteArrayInputStream("Testing".getBytes)))
  val i2 = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(" using".getBytes)))
  // here the instances are not passed to the body
  // couldn't think of a way preserving the type of each instance
  using(i1, i2) {
    print(i1.readLine)
    println(i2.readLine)
  }

  // will throw java.io.IOException: Stream closed
  i1.readLine

  // slightly more useful
  val emf = Persistence.createEntityManagerFactory("persistence_unit")
  using(emf.createEntityManager) { em =>
    // use em here...
  }
}