What data types in Swift are reference types?

In Swift, reference types are classes and closures. They are stored in the heap, and when assigned or passed, a reference to the same object is copied.

Primitive types, structures (struct), and enumerations (enum) are value types, which are copied upon assignment.

Example:

class Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}

let person1 = Person(name: "Ivan")
let person2 = person1
person2.name = "Peter"
print(person1.name) // Will print "Peter" because person1 and person2 refer to the same object