May be stupid but a junior dev here :smile: Is there a particular good reason to have a generic fun...

# android-architecture

[Ofir Bar]

May be stupid but a junior dev here 😄

Is there a particular good reason to have a generic function parameter type inherit from “Any”?

In the image, the method we use, and the second one is without it.

[Drew Hamilton]

In the second one, T can be a nullable type. In the first one, it can’t be.

[wcaokaze]

Yep. In other words, <T> means <T : Any?>

[Ofir Bar]

Hmm.. didn’t expect that.

So by default, Kotlin generics allow nulls.. isn’t that goes against how Kotlin tries to fight NPE?

I would expect <T> to behave such as <T: Any> and to have a null value explicitly use <T: Any?>

@Drew Hamilton @wcaokaze

[Drew Hamilton]

I think either way you’d have to “just know” which one is the default because different people would have different intuitions. But IMO it makes sense because Any? is the lowest common denominator; the most generic available type in the JVM.

[arekolek]

one example where T : Any makes sense:

data class Optional<T : Any>(val value: T? = null)

interface Test {
    fun test(): Optional<String?> // compilation error
}

It's a constraint https://kotlinlang.org/docs/tutorials/kotlin-for-py/generics.html#constraints
so it makes sense that without no constraints it is the most general type

[Ofir Bar]

Got it, that makes sense
thank you!