I have below method in a companion object, which s...

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[Pablichjenkov]

I have below method in a companion object, which should extract a specific implementation class Wrapper depending on the Kotlin primitive type.

fun extractRealClass(valueClass: Class<*>): Class<out PrimitiveWrapper<*>>? {

    return when (valueClass) {
        
        Boolean::class.java -> BooleanWrapper::class.java
        
        Int::class.java -> IntWrapper::class.java

        String::class.java -> StringWrapper::class.java

        else -> null
        
    }

}

// where PrimitiveWrapper is defined as:

open class PrimitiveWrapper<T>(val value: T) {... Above func lives in this class companion}

class BooleanWrapper(value: Boolean) : PrimitiveWrapper<Boolean>(value) { ... }

class IntWrapper(value: Int) : PrimitiveWrapper<Int>(value) { ... }

on another class Entry I have this:

Entry<T: Any?>(
    private val key: String,
    private val clazz: Class<T>
) {

override fun getInstance(): T? {

    // It always return null when calling above mentioned func.
    val primitiveClass: Class<out PrimitiveWrapper<*>>?
                = PrimitiveWrapper.extractRealClass(clazz)

}

}

Whenever I call the PrimitiveWrapper.extractClass(clazz) with the save class info it always return null. I tried many things and no matter what in the when block the coming class always print like int or <http://kotlin.Int|kotlin.Int> but never java.lang.Integer. Could some body shed some light?

[Yago Lasse]

Hey! So, Its because Java primitive wrappers are not objects (nor Kotlin non nullable types are). So it will always show int or <http://kotlin.Int|kotlin.Int> (without '?') but never java.lang.Integer. Try it with a nullable <http://kotlin.Int|kotlin.Int>? and you may get java.lang.Integer

[Pablichjenkov]

Interesting, thanks. I will check that.