스위프트 - 상속

class Vehicle {
    var currentSpeed = 0.0
    var description: String {
        return "traveling at \(currentSpeed) miles per hour"
    }
    func makeNoise() {
        //make a noise
    }
}

class Bicycle: Vehicle {
    var hasBasket = false
}

bicycle.currentSpeed = 15.0
print("Bicycle: \(bicycle.description)")

재정의

class Train: Vehicle {
    override func makeNoise() {
        print("Choo Choo")
    }
}
let train = Train()
train.makeNoise()

재정의 방지