Efficient way to match case object in scala

Question

I want to get Student and employee who works in country India and china

object Countries {
  sealed trait Country {def name: String}
  case object FRANCE extends Country {val name = "FRANCE"}
  case object INDIA extends Country {val name = "INDIA"}
  case object CHINA extends Country {val name = "CHINA"}
  val list = Seq(FRANCE, INDIA, CHINA)
}

def getCountry: Option[Countries.Country] ={
  //some DB call to return country based on some parameters .I assume INDIA here
  Option(Countries.INDIA)
}

case class Student(name: String, id: Symbol = Symbol("Id"))

def getStudentName(name: Option[String]): Option[Student]={
  val std = name
    .filterNot(_.isEmpty)
    .map(Student(_))

  getCountry.collect {
    case Countries.INDIA => std
    case Countries.CHINA => std
  }.flatten              
}

case class Emp(id: Int)

def getEmp(id: Option[String]): Option[Emp] = {
  val emp = id.flatMap(_ => Option(Emp(id.get.toInt)))
  getCountry.collect {
    case Countries.INDIA => emp
    case Countries.CHINA => emp
  }.flatten
}

Is there any efficient way to avoid the repeated code using collect and case matching I have done .

I downvoted because the code is nowhere near compiling, making the question not understandable for me. — C4stor
– C4stor, Commented Sep 18, 2017 at 15:15
what do you mean by "efficient"? Do you mean readability (e.g. not repeating itself) or anything else (e.f. better performing)? — Tzach Zohar
– Tzach Zohar, Commented Sep 18, 2017 at 15:16
@C4stor "nowhere near compiling" is an exaggeration, had one mistake (Country instead of Countries.Country) ... — Tzach Zohar
– Tzach Zohar, Commented Sep 18, 2017 at 15:26

Dima · Accepted Answer · 2017-09-18 15:19:03Z

2

def ifCountry[T](result: => Option[T], countries: Country*) = getCountry
  .filter(countries.toSet)
  .flatMap(_ => result)


def getStudentName(name: Option[String]) = ifCountry(
   name.filterNot(_.isEmpty).map(Student(_)),
   INDIA, CHINA
)

def getEmp(id: Option[String]) = ifCountry(
    id.map(Emp(_)), 
    INDIA, CHINA
}

answered Sep 18, 2017 at 15:19

Dima

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5 Comments

coder25 Over a year ago

can anyone explain result: => Option[T] and :=> symbol in scala

mdm Over a year ago

it is the syntax for by name parameters. That means that the parameter will be evaluated only when needed, not before.

Silvio Mayolo Over a year ago

An argument whose type is => A is an argument whose type is A but which will be passed by name rather than by value. That is, it will be evaluated every time that it occurs in the code, rather than exactly once when the function is called.

C4stor Over a year ago

Another way to see it is you're actually passing a function give an A instead of an instance of A, and this function will be called every time you need it.

Dima Over a year ago

Yes, it is actually just a syntactic sugar for Function0

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