Another one with nullability Let s assume I have a function `fun doSomething input SomeClass lt Concrete gt ` Use case is ``` val localInstance SomeClass lt Concrete gt = doSomething localInstance ``` Should I naively cast local instance to `localInstance as SomeClass lt Concrete gt ` to use this method Assume that I can t change the method

This makes `SomeClass lt Concrete gt ` a subtype of `SomeClass lt Concrete gt `

I think you can do this ```fun doSomething input SomeClass lt out Concrete gt ```

Another one with nullability Let s assume I have a function kotlinlang #announcements

09/12/2018, 11:38 AM

Another one with nullability Let’s assume I have a function

fun doSomething(input: SomeClass<Concrete?>)

. Use case is:

val localInstance: SomeClass<Concrete> = ...
doSomething(localInstance)

Should I naively cast local instance to

localInstance as SomeClass<Concrete?>

to use this method? Assume that I can’t change the method.

:thread-please: 1

09/12/2018, 11:43 AM

Can you change

SomeClass

? It works if you make its type parameter covariant.

class SomeClass<out T>

SomeClass<Concrete>

a subtype of

SomeClass<Concrete?>

09/12/2018, 11:50 AM

LiveData

in this case.

09/12/2018, 11:52 AM

Then this method call cannot be done. The method (

doSomething

) might be trying to put a

null

SomeClass

. If you were to pass in a

SomeClass<Concrete>

that would cause problems.

You need to change either the class or the method.

09/12/2018, 11:55 AM

And what if I’d be able to change the method?

09/12/2018, 11:56 AM

I think you can do this:

fun doSomething(input: SomeClass<out Concrete?>)