chaining on methods with optional return values, linking multiple levels of chaining

// model classes for optional chaining
class Person{
    var residence: Residence?
}

class Residence{
    var rooms: [Room] = []
    var total: Int{
        return rooms.count
    }
    subscript(i: Int) -> Room{
        get{
            return rooms[i]
        }
        set{
            rooms[i] = newValue
        }
    } 
    func printTotal(){
        print("total number of rooms are: \(total)")
    }
    var address: Address?
}

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

class Address{
    var number: String?
    var street: String?
    var buildingName: String?
    func identifier() -> String?{
        if let number = number, let street = street{
            return "\(number) \(street)"
        }
        else if(buildingName != nil){
            return buildingName;
        }
        else {
            return nil
        }
    }
}

// accessing properties through optional chaining

let arthur = Person()
if let roomCount = arthur.residence?.total{
    print("arthur has \(roomCount) rooms in his residence")
}
else{
    print("arthue doesn't have any room.")
}

let someAddress = Address()
someAddress.street = "ny"
someAddress.number = "one"
arthur.residence?.address = someAddress

func createAddress() -> Address{
    let someAddress = Address()
someAddress.street = "ny"
someAddress.number = "one"
return someAddress
}

arthur.residence?.address = createAddress()

// calling methods through optional chaining

if arthur.residence?.printTotal() != nil{
    print("it was possible to print total rooms")
}
else{
    print("print rooms isn't possible yet")
}

if (arthur.residence?.address = someAddress) != nil{
    print("it was possible to set the address")
}
else{
    print("isn't possible to set address")
}

// accessing subscripts through optional chaining

arthur.residence?[0] = Room(name: "haveli")

var finnsHouse = Residence()
finnsHouse.rooms.append(Room(name: "second room"))
finnsHouse.rooms.append(Room(name: "thirs room"))
arthur.residence = finnsHouse

if let firstRoom = arthur.residence?[0].name{
    print("the first room name of arthur is: \(firstRoom)")
}else{
    print("can't retrieve the value of room name")
}

// linking multiple levels of chaining

let arthurAddress = Address()
arthurAddress.buildingName = "brainetics"
arthurAddress.street = "silicon valley"
arthurAddress.number = "1234"
arthur.residence?.address = arthurAddress

if let arthurStreet = arthur.residence?.address?.street{
    print("street name of arthur residence is: \(arthurStreet)")
}
else{
    print("can't retrive the value of street of arthur residence.")
}

// chaining on methods with optional return values
if let building = arthur.residence?.address?.identifier(){
    print("identified building name is: \(building)")
}

// performing furthur optional chaining on methods return values
if let beginWith = arthur.residence?.address?.identifier()?.hasPrefix("The"){
    if beginWith{
        print("arthurs building name begins with \" The \"")
    }
} else {
    print("can't retrive the value of method")
}