when will SAM conversion will be implemented in Kotlin? I mean for Kotlin SAM interfaces

isn't it already here: https://try.kotlinlang.org/#/Kotlin%20Koans/Introduction/SAM%20conversions/Task.kt ?

I think they work from Java code, but if you have kotlin Interface it does not work

By the looks of it it's not a priority, the issue has been open for years..

Unless you need to interact with Java use a

typealias

@Olekss what advantage does a SAM Interface have over a

(T) -> R

?

@Olekss You don't need them in Kotlin, because Kotlin has proper function types.

I guess they might be nice on Android, for example if you use data binding, you won't be able to access the lambda type from layout (so it's kind of the "interacting with Java" case, but indirectly).

the issue is if you want to create an API that is going to be used from both languages, you can't make it in kotlin. if you want an interface as a parameter, you need to make the API in java

@david-wg2 why do you have to create the API in java?

(T) -> R

is just a

Function<T, R>

under the hood and can be used from java just fine

but it's not an interface

so we are back at the question, what advantages does a SAM-Interface have over a simple

(T) -> R

?

you can implement an interface, you can convey intent in the naming of it (and its method)

I wouldn't say implementing an interface is an advantage (Functional types are more flexible, because you don't have to implement anything)

how is it more flexible if it offers a subset of what the other approach offers?

it is more flexible because everything that has the shape

(T) -> R

can be used, doesn't matter if its a top-level function, "static" function or an instance method. Using a SAM-Interface, the method/function has to be wrapped inside an anonymous object (lambda) that implements the Interface

i'll have to get back to this after work 😬

@Andreas Sinz Theoretically functional types are better of course, but in practise they make the API difficult to use from Java. The other alternative are SAM interfaces but those are a pain to use from Kotlin.

what makes it hard to use from java? isn't

(T) -> R

just a

Function<T, R>

?

@Andreas Sinz https://docs.google.com/document/d/1QGRugXflSrYaEpq9BiEjdz2yojF6Ubqh5gUE3IprNnU/edit?usp=sharing

Kotlin SAM lambda conversion is expected in Kotlin 1.3. It has the advantages of not having autoboxing when not inline

so it should be possible to call a functional type with a lambda in java just fine, right?