Accessing type members outside the class in Scala
- by Pekka Mattila
Hi,
I am trying to understand type members in Scala. I wrote a simple example that tries to explain my question.
First, I created two classes for types:
class BaseclassForTypes
class OwnType extends BaseclassForTypes
Then, I defined an abstract type member in trait and then defined the type member in a concerete class:
trait ScalaTypesTest {
type T <: BaseclassForTypes
def returnType: T
}
class ScalaTypesTestImpl extends ScalaTypesTest {
type T = OwnType
override def returnType: T = {
new T
}
}
Then, I want to access the type member (yes, the type is not needed here, but this explains my question). Both examples work.
Solution 1. Declaring the type, but the problem here is that it does not use the type member and the type information is duplicated (caller and callee).
val typeTest = new ScalaTypesTestImpl
val typeObject:OwnType = typeTest.returnType // declare the type second time here
true must beTrue
Solution 2. Initializing the class and using the type through the object. I don't like this, since the class needs to be initialized
val typeTest = new ScalaTypesTestImpl
val typeObject:typeTest.T = typeTest.returnType // through an instance
true must beTrue
So, is there a better way of doing this or are type members meant to be used only with the internal implementation of a class?
