inheritance

import UIKit

class Vehicle {

    var currentSpeed = 0.0;

    //每呼叫一次就會被執行一次

    var description:String {

        return "現在的速度是每小時\(currentSpeed)";

    }

    func makeNoice() {

        //發出聲音

        

    }

}

//Bicycle 繼承 Vehicle

class Bicycle:Vehicle{

    var hasBasket = false;

}

let someVehicle = Vehicle();

let bicycle = Bicycle();

bicycle.currentSpeed = 15.0;

print("Bicycle:\(bicycle.description)");

class Tandem:Bicycle {

    var currentNumberOfPassengers = 0;

}

let tandem = Tandem();

tandem.hasBasket = true;

tandem.currentNumberOfPassengers = 2;

tandem.currentSpeed = 22.0;

//override

//Train 繼承 Vehicle，override method

class Train:Vehicle {

    override func makeNoice() {

        print("Choo Choo");

    }

}

let train = Train();

train.makeNoice();

//Car 繼承 Vehicle，override computed property

class Car:Vehicle{

    var gear = 1;

    override var description: String {

//        return "現在的速度是每小時\(currentSpeed)公里，" + "目前是\(gear)檔";

        return super.description + ",目前是\(gear)檔";

    }

}

let car = Car();

car.currentSpeed = 25.0;

car.gear = 3;

print("Car:\(car.description)");

//override property with observer

class AutomaticCar:Car {

    override var currentSpeed: Double{

        didSet{

            gear = Int(currentSpeed / 10.0) + 1

        }

    }

}

let automatic = AutomaticCar();

automatic.currentSpeed = 35.0;

print("automaticCar.\(automatic.description)");