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VistasIs it possible to provide a generic type constraint to a List in Kotlin?
interface Conditional{
fun isEligible(): Boolean
}
class Super()
class A(): Super(), Conditional
class B(): Super()
I would like to create a list that only contains Super subclasses that have implemented Conditional interface. (Just to help me with some compile-time static type checking)
Compiler would allow me to create this:
val conditionals: List<Super : Conditional> = listOf(A())
But it would not allow me to create this:
val conditionals: List<Super : Conditional> = listOf(A(), B())
I understand you can use generics with classes and function declarations, but how about value declarations?
EDIT
I tried the following but type inference doesn't work well, it seems I'd need to do casting to a specific interface
1 Respuestas
Responde la pregunta0
Unfortunately, intersection types are not denotable yet in Kotlin code (see KT-13108).
However, they are internally supported by the compiler, so you can get away with some generic constructs in some cases.
One option is to use a custom listOf specifically for these types:
fun <T> listOfConditionalSuper(vararg elements: T): List<T> where T: Super, T: Conditional =
listOf(*elements)
You will get proper type inference then:
