工廠方法模式

簡單工廠模式有一個缺點，就是增加子類的時候，需要修改工廠類裡的switch。工廠方法模式可以優化簡單工廠模式的這個缺點。

UML圖：

示例代碼：

public interface ICar
    {
        string GuaDang();
    }       

public class ShouDong:ICar
    {
        public string GuaDang()
        {
            return "我是手動擋";
        }
    }      

public class ZiDong:ICar
    {
        public string GuaDang()
        {
            return "我是自動擋";
        }
    }      

public interface ICarFactory
    {
        ICar GetCar();
    }      

class ShouDongFactory:ICarFactory
    {
        public ICar GetCar()
        {
            return new ShouDong();
        }
    }      

public class ZiDongFactory:ICarFactory
    {
        public ICar GetCar()
        {
            return new ZiDong();
        }
    }      

class Program
    {
        static void Main(string[] args)
        {
            ICarFactory fac = new ShouDongFactory();
            Console.WriteLine(fac.GetCar().GuaDang());

            ICarFactory facA = new ZiDongFactory();
            Console.WriteLine(facA.GetCar().GuaDang());
        }
    }