How to build Kproperty for private fields

Question

can anyone help to answer my questions?

I write the below function which receive the KProperty1<T, *> as a parameter:

fun <T> printProperty(instance: T, prop: KProperty1<T, *>) {
        println("prop : ${prop.get(instance)}")
}

And I also define a Person class:

class Person(val name: String, var age: Int, private var address: String = "") {
       // empty body
}

But when I write the test code, the compile of address property failed,

printProperty(person, Person::name) // Compile success
printProperty(person, Person::age) // Compile success
printProperty(person, Person::address) // Compile failed!!!

Although I know it is because the address field is private and cannot be accessed like Person::address. But is there a way to construct Kproperty for a private field to make it also can be used by the function?

Answer 1

Using Kotlin reflection, you can define your printProperty function in the way that it makes each property accessible before accessing it:

import kotlin.reflect.KCallable
import kotlin.reflect.jvm.isAccessible

fun <T> printProperty(instance: T, prop: KCallable<T>) {
    prop.isAccessible = true
    println("prop : ${prop.call(instance)}")
}

Since Person::address is still private, you would have to access it in a different way:

printProperty(person, Person::name) // public
printProperty(person, Person::age) // public
printProperty(person, Person::class.members.first { it.name == "address" }) // private