Swift学习笔记2---继承(Inheritance)

//
//  main.swift
//  Inheritance
//  继承
//
//  Created by TSUBASA on 15/12/18.
//  Copyright © 2015年 TSUBASA. All rights reserved.
//

import Foundation

// 继承
/**
*  在Swift中，继承是区分【类】与其他类型的一个基本特征
*/

//base class 基类
class Vehicle {
    var currentSpeed = 0.0
    var description: String {
        return "traveling at \(currentSpeed) miles per hour"
    }
    
    func makeNoise() {
        // 什么都不做
    }
}



let someVehicle = Vehicle()
print("Vehicle: \(someVehicle.description)")

/**
*  子类
class SomeSubclass: SomeSuperclass {

}
*/

// 定义一个Vehicle的子类
class Bicycle: Vehicle {
    var hasBasket = false
}
let bicycle = Bicycle()
bicycle.hasBasket = true
bicycle.currentSpeed = 15.0
print("Bicycle: \(bicycle.description)")

// 子类还可被其他类继承，成为父类
// 双人自行车类 继承于 自行车类
class Tandem: Bicycle {
    var currentNumberOfPassengers = 0
}
let tandem = Tandem()
tandem.hasBasket = true
tandem.currentNumberOfPassengers = 2
tandem.currentSpeed = 22.0
print("Tandem: \(tandem.description)")

// Overriding Methods 重写方法
class Train: Vehicle {
    override func makeNoise() {
        print("Choo Choo")
    }
}
let train = Train()
train.makeNoise()

class Car: Vehicle {
    var gear = 1
    override var description: String {
        return super.description + " in gear \(gear)"
    }
}
let car = Car()
car.currentSpeed = 25.0
car.gear = 3
print("Car: \(car.description)")

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)")

/**
*  防止重写 Preventing Overrides
*/

// 使用final特性
// final var, final func, final class func, final subscript
// 如果重写了final方法，属性或下标属性，编译时不会报错。

// 也可以在类前加上final将整个类标记为final的，这样的类无法继承，任何试图继承此类，编译时会报错。