How to copy an object in Kotlin?

@marcella.kautzer 

In Kotlin, you can create a copy of an object using the copy() function, which is a member of the Data class. The copy() function creates a new object with the same property values as the original object, and allows you to specify any properties that you want to change in the new object.

Here's an example of how to use the copy() function to create a copy of an object:

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data class Person(val name: String, val age: Int)

fun main() {
    val originalPerson = Person("Alice", 25)
    val copiedPerson = originalPerson.copy()

    println(originalPerson)  // prints "Person(name=Alice, age=25)"
    println(copiedPerson)  // prints "Person(name=Alice, age=25)"
}

In this example, originalPerson is an instance of the Person class with the name "Alice" and the age 25. The copy() function creates a new Person object with the same name and age as the original object, and assigns it to the variable copiedPerson.

You can also use the copy() function to specify different values for any of the properties in the new object. For example:

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data class Person(val name: String, val age: Int)

fun main() {
    val originalPerson = Person("Alice", 25)
    val copiedPerson = originalPerson.copy(name = "Bob")

    println(originalPerson)  // prints "Person(name=Alice, age=25)"
    println(copiedPerson)  // prints "Person(name=Bob, age=25)"
}

In this example, the copiedPerson object has the same age as the original object, but the name is changed to "Bob".

@marcella.kautzer 

Note that the copy() function only works for classes that are declared as data classes. This function automatically generates a copy function that includes all properties defined in the primary constructor of the data class.

Also, keep in mind that the copy is a shallow copy, meaning that if the object contains any mutable properties or nested objects, they will not be copied independently.

Here's an example demonstrating copying nested objects using the copy() function:

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data class Address(val street: String, val city: String)

data class Person(val name: String, val age: Int, val address: Address)

fun main() {
    val originalPerson = Person("Alice", 25, Address("Main St", "City"))

    val copiedPerson = originalPerson.copy(address = originalPerson.address.copy(street = "New St"))

    println(originalPerson) // prints "Person(name=Alice, age=25, address=Address(street=Main St, city=City))"
    println(copiedPerson) // prints "Person(name=Alice, age=25, address=Address(street=New St, city=City))"
}

In this example, the Person class has a nested Address object. To copy the Address object while also copying the Person object, we use the copy() function on both objects. By specifying the property we want to change (address), we can create a new Person object with the same properties, except for the nested Address object, which will have the modified street value.

It's important to remember that the copy() function returns a new object, so if you want to modify an existing object, you need to assign the copied object back to the same variable.