How do I create an enum from an Int in Kotlin?
enums, kotlin
Solution
`Enum#valueOf` is based on name. Which means in order to use that, you'd need to use `valueof("FOO")`. The `valueof` method consequently takes a String, which explains the error. A String isn't an Int, and types matter. The reason I mentioned what it does too, is so you know this isn't the method you're looking for.
If you want to grab one based on an int value, you need to define your own function to do so. You can get the values in an enum using `values()`, which returns an `Array<Types>` in this case. You can use `firstOrNull` as a safe approach, or `first` if you prefer an exception over null.
So add a companion object (which are static relative to the enum, so you can call `Types.getByValue(1234)` (`Types.COMPANION.getByValue(1234)` from Java) over `Types.FOO.getByValue(1234)`.
companion object {
private val VALUES = values()
fun getByValue(value: Int) = VALUES.firstOrNull { it.value == value }
}
`values()` returns a new Array every time it's called, which means you should cache it locally to avoid re-creating one every single time you call `getByValue`. If you call `values()` when the method is called, you risk re-creating it repeatedly (depending on how many times you actually call it though), which is a waste of memory.
Admittedly, and as discussed in the comments, this may be an insignificant optimization, depending on your use. This means you can also do:
companion object {
fun getByValue(value: Int) = values().firstOrNull { it.value == value }
}
if that's something you'd prefer for readability or some other reason.
The function could also be expanded and check based on multiple parameters, if that's something you want to do. These types of functions aren't limited to one argument.
Problem
I have this `enum`: ``` enum class Types(val value: Int) { FOO(1) BAR(2) FOO_BAR(3) } ``` How do I create an instance of that `enum` using an `Int`? I tried doing something like this: ``` val type = Types.valueOf(1) ``` And I get the error: Integer literal does not conform to the expected type String