thoughtworksinc / extractor.scala

Make PartialFunction and extractors composable

Extractor.scala

Extractor.scala is a library to convert between A => Option[B], PartialFunction[A, B] and extractor objects for pattern matching.

Usage

// Add this line in your build.sbt
libraryDependencies += "com.thoughtworks.extractor" %% "extractor" % "latest.release"

import com.thoughtworks.Extractor._

// Define a PartialFunction
val pf: PartialFunction[Int, String] = {
  case 1 => "matched by PartialFunction"
}

// Define an optional function
val f: Int => Option[String] = { i =>
  if (i == 2) {
    Some("matched by optional function")
  } else {
    None
  }
}

// Convert an optional function to a PartialFunction
val pf2: PartialFunction[Int, String] = Function.unlift(f)

util.Random.nextInt(4) match {
  case pf.extract(m) => // Convert a PartialFunction to a pattern
    println(m)
  case f.extract(m) => // Convert an optional function to a pattern
    println(m)
  case pf2.extract(m) => // Convert a PartialFunction to a pattern
    throw new AssertionError("This case should never occur because it has the same condition as `f.extract`.")
  case _ =>
    println("Not matched")
}

You can also use .extract.seq to extract elements of a sequence data.

import com.thoughtworks.Extractor._

val csvRow: String => Option[Seq[String]] = { line =>
  Some(line.split(','))
}

"foo,bar,baz" match {
  case csvRow.extract.seq(cell0, cell1, cell2) =>
    println(s"cell1=$cell1") // Output: cell1=bar
}

extractor.scala's Issues

intellij reports "cannot resolve symbol extract"

Hi Yang Bo,
I found intellij reported "cannot resolve symbol extract" on line of: case underlying.extract(b) => b in Extractor.OptionFunctionToPartialFunction.unlift.
But the test can be run correctly, so it seems intellij is not smart enought to find out its an implicit conversion, I think.