Enum.valueOf in Kotlin

Question

Is there a way to make something like this work in Kotlin without the reflection?

inline fun <reified T : kotlin.Enum<T>> safeValueOf(type: String?): T? {     return java.lang.Enum.valueOf(T::class.java, type) } 

The example below doesn't compile due to:

Type parameter bound for T in inline fun <reified T : kotlin.Enum<T>> safeValueOf(type: kotlin.String?): T? is not satisfied: inferred type TestEnum? is not a subtype of kotlin.Enum<TestEnum?>

enum class TestEnum  fun main() {     val value: TestEnum? = safeValueOf("test") } 

Answer 1

Your function works if you specify the type parameter value explicitly:

val value = safeValueOf<TestEnum>("test") 

The original code is supposed to work as well, but doesn't work because of a bug in the type inference implementation: https://youtrack.jetbrains.com/issue/KT-11218

Answer 2

Crash-safe Solution

Create an extension and then call valueOf<MyEnum>("value"). If the type is invalid, you'll get null and have to handle it

inline fun <reified T : Enum<T>> valueOf(type: String): T? {     return try {         java.lang.Enum.valueOf(T::class.java, type)     } catch (e: IllegalArgumentException) {         null     } } 

Alternatively, you can set a default value, calling valueOf<MyEnum>("value", MyEnum.FALLBACK), and avoiding a null response. You can extend your specific enum to have the default be automatic

inline fun <reified T : Enum<T>> valueOf(type: String, default: T): T {     return try {         java.lang.Enum.valueOf(T::class.java, type)     } catch (e: IllegalArgumentException) {         default     } } 

Or if you want both, make the second:

inline fun <reified T : Enum<T>> valueOf(type: String, default: T): T = valueOf<T>(type) ?: default