設計模式-工廠方法模式

public interface IYunSuan
    {
        double getResult(int num1, int num2);        
    }
    public class jia : IYunSuan
    {
        public double getResult(int num1, int num2)
        {
            return num1 + num2;
        }
    }
    public class jian : IYunSuan
    {
        public double getResult(int num1, int num2)
        {
            return num1-num2;
        }
    }
    public class cheng : IYunSuan
    {
        public double getResult(int num1, int num2)
        {
            return num1*num2;
        }
    }
    public class chu : IYunSuan
    {
        public double getResult(int num1, int num2)
        {
            if (num2 == 0) return 0;
            return num1/num2;
        }
    }

    //////////////
     //簡單工廠，專門生產對象
        public static IYunSuan createYunSuanObj(string type)
        {
            switch (type)
            {
                case "+":return new jia();
                case "-": return new jian();
                case "*": return new cheng();
                case "/": return new chu();
            }
            return null;
        }
    //工廠方法模式,把簡單工廠分解
    public interface IFactory
    {
        IYunSuan createYunSuanObj();
    }
    public class jiaFactory : IFactory
    {
        public IYunSuan createYunSuanObj()
        {
            return new jia();
        }
    }
    public class jianFactory : IFactory
    {
        public IYunSuan createYunSuanObj()
        {
            return new jian();
        }
    }
    public class chengFactory : IFactory
    {
        public IYunSuan createYunSuanObj()
        {
            return new cheng();
        }
    }
    public class chuFactory : IFactory
    {
        public IYunSuan createYunSuanObj()
        {
            return new chu();
        }
    }

        前端：
        static void Main(string[] args)
        {
            //簡單工廠模式
            //var jia=simpleFactory.createYunSuanObj("+");
            //var result=jia.getResult(1,2);
            //Console.WriteLine(result);
            //Console.ReadLine();
                        //工廠方法模式
            IFactory factory = new jiaFactory();
            var jia=factory.createYunSuanObj();
            var result=jia.getResult(1, 2);
            Console.WriteLine(result);
            Console.ReadLine();
        }

總結：定義一個創建對象的接口，讓子類決定實例化哪個類，工廠模式使得一個類的實例化延遲到其子類。是基于簡單工廠的擴展模式，解耦了簡單工廠的工廠類，符合了幾大原則
優點：解耦
缺點：代碼量增加N多，讓人蛋疼。