设计模式-工厂方法模式

Factory Method Pattern

工厂方法(Factory Method) 定义一个用于创建对象的接口，让子类决定实例化哪一个类，工厂方法使一个类的实例化延迟到其子类。 

工厂方法模式是简单工厂模式的衍生，解决了许多简单工厂模式的问题。首先完全实现‘开－闭
原则’，实现了可扩展。其次更复杂的层次结构，可以应用于产品结果复杂的场合。

示例代码：

    /// <summary>
    /// 运算类
     /// </summary>
    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; }
        }

        /// <summary>
        /// 得到运算结果
        /// </summary>
        /// <returns></returns>
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }

    /// <summary>
    /// 加法类
    /// </summary>
    class OperationAdd : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }

    /// <summary>
    /// 减法类
    /// </summary>
    class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }
    /// <summary>
    /// 乘法类
    /// </summary>
    class OperationMul : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA * NumberB;
            return result;
        }
    }
    /// <summary>
    /// 除法类
    /// </summary>
    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;
        }
    }

    /// <summary>
    /// 工厂方法
    /// </summary>
    interface IFactory
    {
        Operation CreateOperation();
    }

    /// <summary>
    /// 专门负责生产“+”的工厂
    /// </summary>
    class AddFactory : IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationAdd();
        }
    }

    /// <summary>
    /// 专门负责生产“-”的工厂
    /// </summary>
    class SubFactory : IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationSub();
        }
    }

    /// <summary>
    /// 专门负责生产“*”的工厂
    /// </summary>
    class MulFactory : IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationMul();
        }
    }

    /// <summary>
    /// 专门负责生产“/”的工厂
    /// </summary>
    class DivFactory : IFactory
    {
        public Operation CreateOperation()
        {
            return new OperationDiv();
        }
    }

客户端调用：

IFactory operFactory = new AddFactory();
Operation oper = operFactory.CreateOperation();
oper.NumberA = 1;
oper.NumberB = 2;
double result=oper.GetResult();

 

http://blog.csdn.net/zhengzhb/article/details/7348707 

http://www.cnblogs.com/cbf4life/archive/2009/12/20/1628494.html