CODEWITHSUNDEEP
genericskotlin
SilverCorvus
SilverCorvus

Reputation: 3076

References to generic functions

Is it possible to make reference to generic functions in Kotlin?

For example, let's say I have a function:

fun inline <reified T> appendToString(a: T, b: T) = a.toString() + b.toString

How can you reference this function? This will not compile

var a = ::appendToString<Int>

Upvotes: 22

Views: 2632

Answers (2)

Haomin
Haomin

Reputation: 1559

Essentially you have to define the property type and then put generic functions in it. Like Max mentioned it in the question's comment section.

// generic function
fun <T> appendToString(a: T, b: T) = a.toString() + b.toString()

// Failed, since cannot type inference
val temp = ::appendToString

// Failed, invalid syntax, since you cannot use type parameters this way
val temp2 = ::appendToString<String, String>

// Success, valid syntax to define type, unlike previous temp2 example, and resolved the type inference issue in temp1, since you spelled it out for the compiler
val temp3: (String, String) -> String = ::appendToString

Or you can use typealias to do a work around, if you are using function as arguments:

typealias TypedAppendToString = (String, String) -> String

fun <T> appendToString(a: T, b: T) = a.toString() + b.toString()

fun refToFunction(appendToString: TypedAppendToString) {
    appendToString.invoke("daf", "daf")
}

fun main() {
    refToFunction(::appendToString)
}

Upvotes: 9

daemontus
daemontus

Reputation: 1157

Currently it is not supported. But there is a feature request you can support if you would like to see it implemented :) KT-12140

Upvotes: 28

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