My goal is to use Arrow in a java project at our c...

# arrow

[Gopal S Akshintala]

My goal is to use Arrow in a java project at our company ‘Salesforce’
How can I use Kotlin Function type as a Data type within Java? For example:
I have a typealias typealias _Validator_<_ValidatableT_, _FailureT_> = _suspend_ (_ValidatableT_) -> _Either_<_FailureT_, Any?>
Within Kotlin, I use it like this as a data type to assign to a lamda val validateParent3X: _Validator_<_Egg_, _ValidationFailure_> = {...}
But I cannot use typealias from Java. What is the idiomatic way to use this Function type as data type on Java?
I see two unknows I have for java interoperability. 1. How can I idimotically refer a Function type 2. Function type being suspend

[simon.vergauwen]

_Validator_<_ValidatableT_, _FailureT_> should be (_ValidatableT, Continution<Any?>_) -> Any? from Java, no?

[Gopal S Akshintala]

didn’t complete get it, but I see two unknows I have for java interoperability. 1. How can I idimotically refer a Function type 2. Function type being suspend

[Gopal S Akshintala]

My goal is to make use of arrow in a Java project at our company Salesforce, so I am researching on interoperability

[simon.vergauwen]

Afaik if you interopt with suspend from Java it always becomes callback based using Continution

[simon.vergauwen]

Since suspend fun example(i: Int): Int = i + 1 is actually:

[simon.vergauwen]

public Object example(Int i, $cont Continuation<Object>) afaik

[pakoito]

But I cannot use typealias from Java. What is the idiomatic way to use this Function type as data type on Java?

At worst you’d have to write an interface that extends Kotlin’s function interfaces with the parameters Simon has indicated

[pakoito]

() -> A in Java is kotlin.Function0 or something like that

[Gopal S Akshintala]

Got it! I removed suspend for now and Instead of typealias, I used interface

interface Validator<ValidatableT, FailureT> {
    fun validate(validatable: ValidatableT): Either<FailureT, Any?>
}

Now I am able to use it in java this way

Validator<Egg, ValidationFailure> abc = egg -> new Either.Right(new Egg(1, new Yolk(Condition.GOOD, Color.GOLD)));

[pakoito]

great

[pakoito]

do fun interface in Kotlin, you should get SAM too

[Gopal S Akshintala]

I explored them, but they are only useful within Kotlin right?

[Gopal S Akshintala]

I dnt see a use of them over interface

[Gopal S Akshintala]

extra overhead is I had to use name before lambda, like Validator {…}

[Gopal S Akshintala]

Oh! I was wrong about that, my compiler fooled me.. I see there is no way to assign lambda to interface in Kotlin. It has to be a SAM and I have to use it this way

val validate1SimpleX: Validator<Egg, ValidationFailure> = Validator {
    if (simpleRule(it)) true.right() else NO_EGG_TO_VALIDATE_1.left()
}

[pakoito]

I see there is no way to assign lambda to interface in Kotlin

you can with inheritance

[pakoito]

interface Validator<ValidatableT, FailureT, ResultT>: (ValidatableT) -> Either<FailureT, ResultT>

[pakoito]

you can probably throw fun interface there too

[Gopal S Akshintala]

With inheritance I see the same problem

[Marius Kotsbak]

I suspect using Arrow in Java is not so good idea. Have you considered https://www.vavr.io/ instead? It should supply much of the same native to Java.

[Marius Kotsbak]

https://docs.vavr.io/#_validation maybe

[Gopal S Akshintala]

Yes I currently use it, but there doesn't seem to be active development on that project

[simon.vergauwen]

Afaik the developer that used to work on Vavr stopped working on it since he moved away from Java but I'm not 100% sure.

[Marius Kotsbak]

Ah, that is possible. Try to get Salesforce to move your module to Kotlin or Scala then 🙂