CODEWITHSUNDEEP
scalaoverriding
Duh Huh
Duh Huh

Reputation: 139

What does override do here?

What does the override do here? After deleting override, I can still compile the program.

abstract class Animal {
 def name: String
}

class Cat extends Pet {
  override def name: String = "Cat"
}

Adapted from Tour of Scala: Upper Type Bounds: https://docs.scala-lang.org/tour/upper-type-bounds.html

Upvotes: 0

Views: 55

Answers (1)

Alin Gabriel Arhip
Alin Gabriel Arhip

Reputation: 2638

You are right, this is a particular case where removing it does not affect the program. Why override is allowed here is for various flexibility reasons:

  • say you want to add an implementation in the parent class Animal - that would work without affecting the behavior of Cat because you used the prophylactic override in Cat to prevent that idea from affecting your extended class. So the subclass becomes just a little bit less tightly-coupled from your base class in this case.
  • say someone else deletes the abstract method name or renames it in the parent class (without knowing that method is being overridden). This would raise compile errors in all classes that overridden it, to he/she will know that this change should be thoroughly thought before being done, as it will affect the interface and the way clients interact with your code.
  • also it makes the compiler help you catch typos in subclasses: say you created another subclass and add a different method but misspell name for something else, say nme - you'll see that if you used override the compiler will warn you that nme does not override anything in the base class. (Thanks compiler!)
  • for me personally, using override in subclasses acts as a marker so I know that this method is also defined in the base class, without having to manually check the base class, which usually resides in a different file.

So it's more of a "best practice" thing rather than a necessity in this case, and everyone is free to use it as they see fit.

Upvotes: 1

Related Questions