On Sunday, 27 May 2018 at 20:50:14 UTC, IntegratedDimensions
wrote:
The only problem where it can leak is when we treat an cat as
an animal then put in dog food in to the animal, which is valid
when cat as treated as an animal, then cast back to cat. Now
cat has dog food, which is invalid.
It sounds like you don't want to have a `food` setter in the
`Animal` base class. Instead, you want setters in each child
class that take the specific type required, and possibly an
abstract getter in the base class. You could use a mixin to ease
the process of defining appropriate food types, and you could
have a method that takes the base `Food` class and does runtime
validation.
You might also change `Animal` to `Animal!(TFood : Food)` and go
from there. You'd likely need to extract another base class or
interface so you can have a collection of arbitrary animals.
