Hi guys, I have a enum class and I want to find the enum.

enum class Stage(val title: String) {
    ONE("one"),
    TWO("two");

    companion object {
        // 1st option
        fun fromTitle(title: String)  {
            values().firstOrNull { it.title.equals(title, true) }
        }

        // 2nd option
        private val mapByTitle = Stage.values().associateBy(Stage::title)
        fun fromTitle(title: String) = mapByTitle[title.lowercase()]
    }
}

which one is better in options?

It depends on whether

Stage.fromTitle

is going to be called frequently enough that performance is an important consideration. If not, then option 1 will be sufficient. The call to

values()

creates a new array every single time it's called, but if performance is not a concern, it doesn't matter. In Kotlin 1.9, this issue will go away - see https://youtrack.jetbrains.com/issue/KT-48872. You will then be able to do it this way:

fun fromTitle(title: String) = entries.firstOrNull { it.title.equals(title, true) }

without worrying about creating a new array each time. Using a

Map

is not going to bring much (if any) performance benefit over iterating for the typically small number of entries in an enum.

Perfect thanks

You could also use the valueOf(title.uppercase) method if your title is the same as the enum name