工厂模式的一些个人改进if else

Posted 2020-09-02

关于设计模式，园子有太多的介绍了，我就不去摆文弄墨了。

关于工厂模式，算是最简单，最好理解的设计模式了，当然，可能是最多的设计模式了。我这里说的并不是这个模式的用法，或者见解，这是个人对于这个模式的一些用法的改进而已。

好了，入正题。想必，可能大多数人写工厂模式的代码都是如此。但是，如果再增加一个IPlant的类，就必须地增加if条件判断。对于我这种对代码有洁癖的人，实在受不了。

namespace FactoryMode
{
    class Program
    {
        static void Main(string[] args)
        {
            var plant = PlantFactory.GetPlant("Jd");
        }
    }

    public interface IPlant
    {
        void DownLoad();

        void SendBackMsg();
    }

    public class PlantFactory
    {
        public static IPlant GetPlant(string plantName)
        {
            if (plantName == "Jd")
                return new JdPlant();
            if (plantName == "Tb")
                return new TbPlant();
            else
                return null;
        }
    }


    public class JdPlant : IPlant
    {

        public void DownLoad()
        {
            Console.WriteLine("Jd_DownLoad");
            //throw new NotImplementedException();
        }

        public void SendBackMsg()
        {
            Console.WriteLine("Jd_SendBackMsg");
            //throw new NotImplementedException();
        }
    }

    public class TbPlant : IPlant
    {
        public void DownLoad()
        {
            Console.WriteLine("Tb_DownLoad");
            //throw new NotImplementedException();
        }

        public void SendBackMsg()
        {
            Console.WriteLine("Tb_SendBackMsg");
            //throw new NotImplementedException();
        }
    }
}
改进后的代码:

namespace FactoryMode
{
    class Program
    {
        static void Main(string[] args)
        {
            var plant = PlantFactory.GetPlant("Jd");
        }
    }

    public interface IPlant
    {
        void DownLoad();

        void SendBackMsg();
    }

    public class PlantFactory
    {
        private static Dictionary<string, Type> plantDictionary = new Dictionary<string, Type>();

        public PlantFactory()
        {
            plantDictionary.Add("Jd", typeof(JdPlant));
            plantDictionary.Add("Tb", typeof(TbPlant));

        }
        public static IPlant GetPlant(string plantName)
        {
            IPlant plant = null;
            if (plantDictionary.Keys.Contains(plantName))
            {
                plant = (IPlant)Activator.CreateInstance(plantDictionary[plantName]);
            }
            return plant;
        }
    }


    public class JdPlant : IPlant
    {

        public void DownLoad()
        {
            Console.WriteLine("Jd_DownLoad");
            //throw new NotImplementedException();
        }

        public void SendBackMsg()
        {
            Console.WriteLine("Jd_SendBackMsg");
            //throw new NotImplementedException();
        }
    }

    public class TbPlant : IPlant
    {
        public void DownLoad()
        {
            Console.WriteLine("Tb_DownLoad");
            //throw new NotImplementedException();
        }

        public void SendBackMsg()
        {
            Console.WriteLine("Tb_SendBackMsg");
            //throw new NotImplementedException();
        }
    }
}