Scala - Trait returns different objects

Question

I have a question about traits in Scala.

I have a trait returns a type of object (AA or BB) depending on the value of parameter country.

My implementattion covers the following approach:

trait firstT{

  def GetType(country: String) : OType =  {
      //i would like to call OType.load(country)
  }
}


  trait OType[T <: OType[T]] {
        def load(country: String): OType[T] = ??? 
        //I would like to return AA or BB depending on country
    }

class AA extends OType[AA] {
  override def load(country: String): AA = new AA
}



class BB extends OType[BB] {
  override def load(country: String): BB = new BB
}

Could you please help me on this? Thank you Best Regards

Answer 1

load is a "static" method of the trait so it belongs in the companion object not the class definition.

So the code you want might look like this

trait firstT {
  def GetType(country: String): OType = {
    OType.load(country)
  }
}

trait OType

object OType {
  def load(country: String): OType =
    if (country == "AA") {
      AA.load()
    } else {
      BB.load()
    }
}

class AA extends OType

object AA {
  def load(): AA = new AA
}

class BB extends OType

object BB {
  def load(): BB = new BB
}

If you really need the OType trait to be parameterised by type then use an abstract type member:

trait OType {
  type T <: OType
}

class AA extends OType {
  type T = AA
}

class BB extends OType {
  type T = BB
}