基类
import UIKit
// 基类
class Vehicle {
var currentSpeed = 0.0
var description: String {
return "traveling at \(currentSpeed) miles per hour"
}
func makeNoise() {
}
}
let SomeVehicle = Vehicle()
print("Vehicle: \(SomeVehicle.description)")
console log 如下
定义基类.png
子类
// 子类
class Bicycle: Vehicle {
var hasBasket = false
}
let bicycle = Bicycle()
bicycle.hasBasket = true
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
print("Tandem: \(tandem.description)")
console log 如下
定义子类.png
重写方法
// 重写方法
class Train: Vehicle {
override func makeNoise() {
print("Choo Choo")
}
}
let train = Train()
train.makeNoise()
console log 如下
重写方法.png
重写计算属性
// 重写计算属性
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)")
console log 如下
重写计算属性.png
重写属性监听
// 重写属性监听
class AutomaticCar: Car {
override var currentSpeed: Double {
didSet {
gear = Int(currentSpeed / 10.0) + 1
}
}
}
let automic = AutomaticCar()
automic.currentSpeed = 35.0
print("AutomaticCar: \(automic.description)")
console log 如下
重写属性监听.png
注意: 用final 关键字来阻止重写
