Why not finally allow bracket-less top-level keywords?

[deadalnix]

Le 19/03/2012 21:39, F i L a écrit :
> deadalnix wrote:
>> That is totally broken design. The fact that mothership inherit from
>> ship is a pretty good example of misusing inheritance. The fireMissle
>> is useless unless you KNOW that you are manipulating a MotherShip, so
>> you totally break all the abstraction the OOP could provide.
>
> Other objects can contain references to MotherShip types directly, while
> the main update loop works with the base type. Or, perhaps more
> relevant, an object could execute "fire()" on a list of Ships, which
> MotherShip can be a part of because it IS a Ship, regardless if weather
> it can overwrite Ship's functions or not. I can't imagine a different
> way of defining this relationship short of inheriting from a common
> interface which would require duplicating the fire() function in both
> types (given that fire() is designed to ensure common behavior among all
> Ship types).
>

As all functionnality of a Ship are final, you basically ends up with a 
mother ship that is a ship and then have some other function that are de 
facto separated and unreachable from ship. Separation of concerns tells 
us that this should be 2 different objects.

> This is not a broken concept at all. I'm always open to different ideas,
> but I'm fairly surprised you're arguing this case. Being able to extend
> a type, even when the extensions are entirely additive, is a fundamental
> principle of OOP design.

As teha ddition of MotherShip to Ship are orthogonal, I would argue that 
mothership functionality is better suited for its own 
class/struct/whatever, and agregated with a ship.

The whole « is a » thing is largely misunderstood. See 
http://www.objectmentor.com/resources/articles/lsp.pdf for example.