工厂方法模式

 

    public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;

        public double NumberA
        {
            get { return _numberA; }
            set { _numberA = value; }
        }

        public double NumberB
        {
            get { return _numberB; }
            set { _numberB = value; }
        }

        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }

 

    class OperationAdd : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    

 

    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }

 

    class OperationMul : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }

 

    class OperationDiv : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (NumberB == 0)
                throw new Exception("除数不能为0。");
            result = NumberA / NumberB;
            return result;
        }
    }

 

    interface IFactory
    {
        Operation CreateOperation();
    }

 

    class AddFactory:IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationAdd();
        }
    }

 

    class SubFactory:IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationSub();
        }
    }

 

    class MulFactory:IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationMul();
        }
    }

 

    class DivFactory:IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationDiv();
        }
    }

 

    class Client
    {
        static void Main(string[] args)
        {
            IFactory operFactory = new AddFactory();
            Operation oper = operFactory.CreateOperation();
            oper.NumberA = 1;
            oper.NumberB = 2;
            double result = oper.GetResult();
            Console.WriteLine(result);
        }
    }

 

小结：

• 模式分析：工厂方法模式是类的创建模式，主要实现的是定义一个创建产品对象的工厂接口，将实际创建工作推迟到子类中。工厂方法模式有一个别名叫多态性工厂模式，因为具体工厂类都有共同的接口或共同的抽象父类。
• 优点：核心的工厂类不再负责所有产品的创建，仅仅负责给出具体工厂必须实现的接口，而不接触哪一个产品类被实例化这种细节，使得工厂方法模式可以允许系统在不修改工厂角色的情况下引进新产品。当系统扩展需要添加新的产品对象时，仅仅需要有添加一个具体对象以及一个具体工厂对象，原有工厂对象不需要进行任何修改，符合“开放－封闭”原则。