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Options in Scala

An Option is a data type in Scala that indicates the presence or absence of some data. It can be an instance of either a case class called Some or a Singleton object called None. An instance of Some can store data of any type. An instance of None the object represents the absence of data.

One of the common uses of this is to prevent from getting an NullPointerException in Scala. When mapping an Option without a value (None), the mapping function will just return another None. 

 //Assign cost as Option which means it can be either None when empty
 scala> val cost: Option[Double] =None
 cost: Option[Double] = None

 scala> val fee = 1.25
 fee: Double = 1.25

 scala> cost.flatMap { x => if( x> 1.00) None else Some(x+fee) }
 res18: Option[Double] = None

 //Asssigning value to cost after which its value will be 0.5
 scala> val cost = Some(0.5)
 cost: Some[Double] = Some(0.5)

 scala> cost.flatMap { x => if( x> 1.00) None else Some(x+fee) }
 res19: Option[Double] = Some(1.75)

Another example of Option.

 def matchColorCode(color: String) : Option[Int] = {

  color match {
  case "red" => Some(1)
  case "blue" => Some(2)
  case "green" => Some(3)
  case _ => None
      }
 }

 //color "orange" is not defined
 val code = colorCode("orange")

 code match {

  case Some(c) => println(" code for orange is: "+c)
  case None = > println(" Code not defined for orange")
 }

Let’s look at another value.

 
 val cMap = Map("a" -> 42 ,"b" -> 43)


 def getMapValues(keyValue: String):String = {
    cMap get keyValue match {  //Gets the Value which is passed 
    through the Function
    case Some(mb) => "value found: " +mb
    case None => "No Value Found"
  }

 }

 getMapValues("b") //Value Found 43
 getMapValues("c") //No Value Found

Another way to get Map Values using the combinator method of the Option Class 

 
 def getMapValuesC(s:String)= cMap.get(s).map("Value Found: "+ _)
 .getOrElse("No Value Found")

 getMapValuesC("a")  //Gets the Value 42
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