Resolving resources in a weird, Kotlin-y way

StringResolving.kt

var resources: Resources? = null

val something by R.string.abc_capital_off<String>()

private inline operator fun <reified T> Int.invoke(): ReadOnlyProperty<Any, T> {
    return when {
        String is T -> StringResolvingDelegate(this)
        else -> throw IllegalArgumentException("Unexpected resource type")
    } as ReadOnlyProperty<Any, T>
}

inner class StringResolvingDelegate(private val id: Int): ReadOnlyProperty<Any, String> {
    private var value: String? = null

    override fun getValue(thisRef: Any, property: KProperty<*>): String {
        if (value == null) {
            value = resources?.getString(id) ?: throw IllegalStateException("Resources are null")
        }

        return value!!
    }
}