【C#语言入门】20. 重写，多态

【C#语言入门】20. 重写，多态

一、重写

• 类成员的“纵向扩展”（行为改变，版本增高）
• 重写发生条件：函数成员，可见，签名一致

二、多态（polymorphism）

• 基于重写机制（virtual——》override）
• 函数成员的具体行为（版本）由对象决定

class Program
{
    static void Main(string[] args)
    {
        var car = new Car();
        car.Run();
        var v1 = new Vehicle();
        v1.Run();
        Car c = new RaseCar();
        c.Run();//跟着实例类型走

        Vehicle vc = new Vehicle();
        vc.Run();
        Console.WriteLine(vc.Speed);

        Vehicle vc1 = new Car();
        vc1.Run();
        Console.WriteLine(vc1.Speed);
    }
}

class Vehicle
{
    private int _speed;

    public virtual int Speed
    {
        get { return _speed; }
        set { _speed = value;}
    }
    public virtual void Run()
    {
        Console.WriteLine("I am running.");
    }
}

class Car : Vehicle
{
    private int _rpm;

    public override int Speed
    {
        get { return _rpm / 100; }
        set { _rpm = value * 100; }
    }
    public override void Run()
    {
        Console.WriteLine("Car is running.");
        _rpm = 5000;
    }
}

class RaseCar : Car
{
    public override void Run()
    {
        Console.WriteLine("Rase car is running.");
    }
}