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

# announcements

[muralimohan962]

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


fun main() {
val person1 = Person("Murali", 21)
val person2 = person1.copy()

}

Now my question is do the fields in both person1 and person2 refer to the same objects?

I mean person1.age === person2.age ?

[Hamza]

in the future, please use code snippets, or atleast add your code between\ 3 back ticks

[muralimohan962]

Thanks!

[Hamza]

and no, they don’t

[muralimohan962]

Typing from phone!

[Hamza]

then you can click the + and add a “code snippet” 🙂

[muralimohan962]

Was not familiar with that feature

[muralimohan962]

But the boolean expression gives true

[Hamza]

hmm, i must be wrong then. it should make sense they are not the same

[Hamza]

i’ll let someone else explain

[karelpeeters]

You happened to choose two of the worst types to test this with, String and Int are both special cases.

[karelpeeters]

But yes, they always will point to the same objects. copy isn't magically a deep copy, it only copies the object itself, not the contents of the fields.

[muralimohan962]

But i did test with different types but this seems no different than clone().

[muralimohan962]

Thanks @karelpeeters!

[gcx11]

@karelpeeters @muralimohan962 Actually, copy makes in fact deep copy, see https://kotlinlang.org/docs/reference/data-classes.html#copying

As for referential equality

person1.age === person2.age

is True, but that doesn't mean that variables point to same object, it gets translated to

==

for value types, see https://kotlinlang.org/docs/reference/equality.html#referential-equality

[karelpeeters]

Nope it does definitely not make a deep copy.

[karelpeeters]

=== and == are indeed the same for primitives, but that's not really relevant here.

[gcx11]

Ok, my points is, copy does not return same object, it creates new one

[karelpeeters]

Yes, it creates a shallow copy.