C#学习笔记-工厂模式

题目：计算器

解析：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。

定义运算类：

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;
        }
    }

继承于运算类的具体运算的实现：

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;
        }
    }

工厂方法，接口：

interface IFactory
    {
        Operation CreateOperation();
    }

工厂方法，分别子类：

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

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

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

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

主函数：

static void Main(string[] args)
        {
            //工厂模式自己内部确定了改实例化哪个类，所以要发生变动，只需要在最外面这个地方变动即可
            IFactory operFactory = new AddOperation();

            Operation oper = operFactory.CreateOperation();
            oper.NumberA = 9;
            oper.NumberB = 5;
            double result = oper.GetResult();

            Console.WriteLine(result);

            Console.Read();
        }

注：文中所有代码及知识点均来自于《大话设计模式》,本人属于边学边看边敲代码边总结的阶段。