How to clone object in Kotlin?

For a data class, you can use the compiler-generated copy() method. Note that it will perform a shallow copy.

To create a copy of a collection, use the toList() or toSet() methods, depending on the collection type you need. These methods always create a new copy of a collection; they also perform a shallow copy.

For other classes, there is no Kotlin-specific cloning solution. You can use .clone() if it suits your requirements, or build a different solution if it doesn't.

You can use Gson library to convert the original object to a String and then convert back that String to an actual Object type, and you'll have a clone. Although this is not the intended usage of the Gson library which is actually used to convert between JSON and other object types, but I have devised this method to solve the cloning problem in many of my Kotlin based Android applications. See my example. Put this function in the class/model of which you want to create a clone. In my example I'm cloning an Animal type object so I'll put it in the Animal class

class Animal{
 fun clone(): Animal 
 {
   val stringAnimal = Gson().toJson(this, Animal::class.java)
   return Gson().fromJson<Animal>(stringAnimal, Animal::class.java)
 }
}

Then use it like this:

val originalAnimal = Animal()
val clonedAnimal = originalAnimal.clone()

A Kotlin data class is easy to clone using .copy()

All values with be shallow copied, be sure to handle any list/array contents carefully.

A useful feature of .copy() is the ability to change any of the values at copy time. With this class:

data class MyData(
    val count: Int,
    val peanuts: Int?,
    val name: String
)
val data = MyData(1, null, "Monkey")

You could set values for any of the properties

val copy = data.copy(peanuts = 100, name = "Elephant")

The result in copy would have values (1, 100, "Elephant")

If the class you are trying to clone does not implement Cloneable or is not a data class and is a part of an outside library, you can create an extension method that returns a new instance. For example:

class Person {
  var id: String? = null
  var name: String? = null
} 
fun Person.clone(): Person {
  val person = Person()
  person.id = id
  person.name = name
  return person 
}

It requires to implement Cloneable for your class then override clone() as a public like:

public override fun clone(): Any {<your_clone_code>}

https://discuss.kotlinlang.org/t/how-to-use-cloneable/2364/3

How to clone object in Kotlin?

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