Deep copy of list with objects in Kotlin
That's bacause you are adding all the object references to another list, hence you are not making a proper copy, you have the same elements in two list. If you want diferents list and diferent references, you must clone every object in a new list:
public data class Person(var n: String)
fun main(args: Array<String>) {
//creates two instances
var anna = Person("Anna")
var Alex =Person("Alex")
//add to list
val names = arrayOf(anna , Alex)
//generate a new real clone list
val cloneNames = names.map{it.copy()}
//modify first list
cloneNames.get(0).n = "Another Anna clone"
println(names.toList())
println(cloneNames.toList())
}
[Person(n=Anna), Person(n=Alex)]
[Person(n=Another Anna clone), Person(n=Alex)]
var oldList: List<ClassA>?
val newList = oldList.map { it.copy() }
This is not related to kotlin, when you are adding the objects from the old list to the new one, it add the reference to them (no createing a new object ), whats mean it just copying the address in the memory to the new list.
To fix this problem you should create a new instance for each object. you can create a copy constructor, for example:
constructor(otherA: ClassA) {
this.prop1 = otherA.prop1
this.prop2 = otherA.prop2
...
}
and then add them one by one to the new list:
list1.forEach { list2.add(Class(it)) }