Kotlin 对泛型函数的引用

发布于08月27日

可以引用Kotlin中的泛型函数吗？

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>

推荐答案

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

或者，如果使用函数作为参数，可以使用typealias进行变通:

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)
}