reflection - 获取可空类型的类

Question

我试图匹配可空类型 String?在 Kotlin 反射(reflection)练习中:

data class Test(a: String, b: String?)
val test = Test("1", "2")
val properties = test::class.declaredMemberProperties
val propertyNames = properties.joinToString(",") { 
        when (it.returnType) {
            String?::class.createType() -> "string?"
            String::class.createType() -> "string"
            else -> throw Exception()
        }
}

唉，它因错误而失败，Type in a class literal must not be nullable , 为 String?::class .

Answer 1

createType函数有一个可选的可为空的参数，当我测试它时似乎可以工作。

import kotlin.reflect.full.*

String::class.createType(nullable = true) -> "string?"