kotlin - 是否可以在 Kotlin 的集合过滤中使用功能接口(interface)？

Question

以下代码编译:

val collection = listOf("a", "b")
val filter = { x: String -> x.isEmpty() }
collection.filter(filter)

是否可以使用函数接口(interface)定义过滤器？
例如以下代码无法编译:

fun interface MyFilter {
    fun execute(string: String): Boolean
}

和

val filter = MyFilter { x -> x.isEmpty() }

给出编译错误

Type mismatch.
Required:
(TypeVariable(T)) → Boolean
Found:
MyFilter

Answer 1

你可以继承MyFilter来自 (String) -> Boolean

fun interface MyFilter : (String) -> Boolean

fun main() {
    val collection = listOf("a", "b")
    val filter = MyFilter { x -> x.isEmpty() }
    val newCollection = collection.filter(filter)
}

使用您的自定义方法:

fun interface MyFilter : (String) -> Boolean {
    override operator fun invoke(p1: String): Boolean = execute(p1)
    fun execute(param: String): Boolean
}

但它仅适用于 jvmTarget = 1.8 (or higher)和 -Xjvm-default=all