Какие есть проблемы в коде №1

swiftimport Foundation

class Person {
    var name: String
    var pet: Pet?

    init(name: String) {
        self.name = name
    }
}

class Pet {
    var name: String
    weak var owner: Person?

    init(name: String) {
        self.name = name
    }
}

var john = Person(name: "John")
var dog = Pet(name: "Buddy")

john.pet = dog
dog.owner = john