Is it possible from a variable containing a class ...

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[Wesley Acheson]

Is it possible from a variable containing a class to list the possible value if the class extends enum

[Shawn]

just want to clarify, is value in this example supposed to be an instance of Class<*> or are you attempting to match the type of value in the when expression?

[Giorgos Neokleous]

Yes. you can either have an exchaustive when

when (value) {
   ...
   Enum.VALUE_ONE::class.java -> "A Enum Value 1"
   Enum.VALUE_TWO::class.java -> "A Enum Value 2"
}

or

when (value) {
   ...
    Enum::class.java -> value.enumConstants.first { it::class.java == value }.name
}

[Shawn]

if the content of value is YourEnum::class.java then I don’t believe you’ll be able to match against Enum::class.java

[Shawn]

but I might be misunderstanding the question

[Wesley Acheson]

@Shawn I'm actually trying to catch an exception from jackson. When converting from Json it has a targetType field on InvalidFormatException.

So baically I'm trying to list the possible values when someone enters a bad value. So value is the class.

[Wesley Acheson]

Yeah you are right here. I was trying to simplify. code currently looks like this.

val type: String = if (formatException.targetType == String::class.java) "a String"
                else if (formatException.targetType == BigDecimal::class.java) "a Number"
                else if (formatException.targetType == ZonedDateTime::class.java) "a Date"
                else if (Enum::class.java.isAssignableFrom(formatException.targetType)) "a value of type ${formatException.targetType.simpleName}"
                else formatException.targetType.simpleName

but I was hoping to change back to a when when I got the values nailed down.

something like

val type: String = when {
                    formatException.targetType == String::class.java -> "a String"
                    formatException.targetType == BigDecimal::class.java -> "a Number"
                    formatException.targetType == ZonedDateTime::class.java -> "a Date"
                    Enum::class.java.isAssignableFrom(formatException.targetType) -> "a value of type ${formatException.targetType.simpleName}" // Possible values here.
                    else -> formatException.targetType.simpleName
                }

[Shawn]

You can definitely clean this up a bit with a when, but the ability to print all the possible values is entirely predicated on whether or not Jackson gives you a Class<*> more specific than Class<Enum>

[Wesley Acheson]

I think the signature is class<*>