trait MyTrait {
   def getValue:String
}

class SomeClass {
   def getValue:String = [concrete implementation]
}

class MyClass extends SomeClass with MyTrait

abstract class AbstractOtherClass {
   val mainObject:MyTrait
}

class OtherClass extends AbstractOtherClass {
   val mainObject:MyTrait = new MyClass

   def something = {
      println(mainObject.getValue)  // shall call SomeClass.getValue
   }
}