Question

I don’t understand. Why does Scala support override method as field:

abstract class A {
    def i: Int;
}

class B extends A {
    val i = 123;
}

val obj:A = new B();

println(obj.i)

Method i is as field i. Why?

Answer 1

One quick way to see what’s going on here is to compile this code and use javap to inspect the resulting classes. Here we get the following for A:

public abstract class A implements scala.ScalaObject {
  public abstract int i();
  public A();
}

And for B (with -p, so we see any private members):

public class B extends A implements scala.ScalaObject {
  private final int i;
  public int i();
  public B();
}

So the val just ends up as a private field with a getter—much like what you’d write in idiomatic Java, although the naming convention is different (and isn’t really a convention, since the compiler handles it for you).