Automatic Resource Management

Arm.scala

/**
  * Monad to work with AutoClosables
  * Automatic Resource Management
  * 
  * Example:
  * val lines = Arm(new FileInputStream("/my.txt")).map { stream =>
  *   Source.fromInputStream(stream)("UTF-8").getLines
  * }
  * 
  */

object Arm {
  def apply[A <: AutoCloseable](c: A) = new AutoCloseableWrapper(c)
}

class AutoCloseableWrapper[A <: AutoCloseable](protected val c: A) {
  def map[B](f: (A) => B): B = {
    try {
      f(c)
    } finally {
      c.close()
    }
  }

  def foreach(f: (A) => Unit): Unit = map(f)

  // Not a proper flatMap.
  def flatMap[B](f: (A) => B): B = map(f)

  // Hack :)
  def withFilter(f: (A) => Boolean) = this
}