val and object inside a scala class?

Question

What is the difference between declaring a field as val, lazy val and object inside a scala class, as in the following snippet:

<

Answer 1

One major difference is that val's can be overriden while objects can't.

class C extends B {                           
  override val a1 = new A { def foo = 2 }     
  override object a2 extends A { def foo = 2 }
}

leads to:

:9: error: overriding object a2 in class B of type object C.this.a2;
object a2 cannot be used here - classes and objects cannot be overridden
override object a2 extends A { def foo = 2 }