optional_07.swift

class Street {
    var streetName: String?
}
class House {
    var noOfRooms = 1
    var street: Street?
}
class Person {
    var house: House?
}

let street = Street()
street.streetName = "Adeyeye"

let house = House()
house.street = street

let me = Person()
me.house = house