learning scala PartialFunction

Partial函数的定义

scala> val isveryTasty: PartialFunction[String, String] = { case "Glazed Donut" | "StrawBerry Donut" => "Very Tasty"}
isveryTasty: PartialFunction[String,String] = <function1>

scala> isveryTasty("Glazed Donut")
res3: String = Very Tasty

 

Partianl函数的组合使用：

 

code :

 

  println("\nStep 1: How to define a Partial Function named isveryTasty")
  val isveryTasty: PartialFunction[String, String] = { case "Glazed Donut" | "StrawBerry Donut" => "Very Tasty"}



  println("\nStep 2: How to call the Partial Function named isveryTasty")
  println(s"Calling partial function isveryTasty = ${isveryTasty("Glazed Donut")}")
  // NOTE: you will get scala.MatchError



  println("\nStep 3: How to define PartialFunction named isTasty and unkNownTaste")
  val isTasty: PartialFunction[String, String] = {
    case "Plain Donut" => "Tasty"
  }

  val unkNownTaste: PartialFunction[String, String] = {
    case donut @ _ => s"UnkNown taste for donut = $donut"
  }



  println("\nStep 4: How to compose PartialFunction using orElse")
  val donutTaste = isveryTasty orElse isTasty orElse unkNownTaste
  println(donutTaste("Glazed Donut"))
  println(donutTaste("Plain Donut"))
  println(donutTaste("Chocolate Donut"))

result:

Step 1: How to define a Partial Function named isveryTasty

Step 2: How to call the Partial Function named isveryTasty
Calling partial function isveryTasty = Very Tasty

Step 3: How to define PartialFunction named isTasty and unkNownTaste

Step 4: How to compose PartialFunction using orElse
Very Tasty
Tasty
UnkNown taste for donut = Chocolate Donut