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Re: Can I override a field with a method?
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Posted: Jan 19, 2009 4:56 PM
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No, but you can do it the other way around. You can override a parameterless method with a val field.
scala> class Super {
| private val generator = new Random
| def length: Int = generator.nextInt
| }
warning: there were deprecation warnings; re-run with -deprecation for details
defined class Super
scala> val a = new Super
a: Super = Super@9babc
scala> a.length
res4: Int = 159125958
scala> a.length
res5: Int = 1789171216
scala> a.length
res6: Int = 1404266232
scala> class Sub extends Super {
| override val length: Int = 7
| }
defined class Sub
scala> val b = new Sub
b: Sub = Sub@51e3be
scala> b.length
res7: Int = 7
scala> b.length
res8: Int = 7
The reason you can't override a field with a method is that a method can produce a different value each time, though it isn't required to. Thus a val that always produces the same value can be a valid "implementation" of a method. But if the superclass has a val, then that's supposed to always be the same value, and so it wouldn't be safe to let people override them with defs that could return a different value each time (as well as have side effects each time).
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