オーバーライド

/* オーバーライド */
class Car: Vehicle {
    var speed: Double = 0.0
    override init() {
        super.init()
        maxPassengers = 5
        numberOfWheels = 4
    }
    override func description() -> String {
        return super.description() + "; "
            + "traveling at \(speed) mph"
    }
}
 
var car = Car()
print(car.description())
car.speed = 30.0
print(car.description())