Example of copy-on-write behavior in Swift

CoW.swift

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

struct PersonCOW {
    private var person: Person
    
    init(name: String) {
        person = Person(name: name)
    }
    
    var name: String {
        get {return person.name}
        set {
            if !isKnownUniquelyReferenced(&person) {
                person = Person(name: newValue)
                print("Making a copy")
                
            }
            person.name = newValue
        }
    }
}