Hello World

I learned a lot from anonymous programmers on their blogs, articles and forums. Time to give something back.

Today I was trying to make a safe navigation operator in Scala. The idea is to use Option instead of reference with possible null value.

implicit class SafeNavigation[A](o: Option[A]) {
  def ?[B](a: A => Option[B]): Option[B] = if (o.isEmpty) None else a(o.get)
}

class Test1(s: String) {
  var f: Option[String] = Some(s)
  var f2: Option[String] = None
  val t2: Option[Test2] = Some(new Test2(1))
  val t2b: Option[Test2] = None
}

class Test2(i: Int) {
  def f: Option[Int] = Some(i)
  def f2: Option[Int] = None
}

val x2: Option[Test1] = None
x2?(_.f)?(s => Some(s.length))    // None

val x3 = Some(new Test1("test"))
x3?(_.f)?(s => Some(s.length))      // Some(4)
x3?(_.f2)?(s => Some(s.length))     // None

x3 ? (_.t2) ? (_.f) ? (i => Some(i+2)) ?
  (i => if (i > 0) Some(i.toString + " int") else None)   // Some(3 int)
x3?(_.t2)?(_.f2)?(i => Some(i+2))     // None