简单工厂模式

1. 简介

从设计模式的类型上来说，简单工厂模式是属于创建型模式，又叫做静态工厂方法（Static Factory Method）模式，但不属于23种GOF设计模式之一。简单工厂模式是由一个工厂对象决定创建出哪一种产品类的实例。简单工厂模式是工厂模式家族中最简单实用的模式，可以理解为是不同工厂模式的一个特殊实现。

2. 代码示例

//运算类
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;
        }
}
//加减乘除类
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("除数不能为零");
            result = NumberA / NumberB;
            return result;
        }
}
//简单运算工厂类
public class OperationFactory
    {
        public static Operation createOprate(string operate)
        {
            Operation oper = null;
            switch (operate)
            {
                case "+":
                    oper = new OperationAdd();
                    break;
                case "-":
                    oper = new OperationSub();
                    break;
                case "*":
                    oper = new OperationMul();
                    break;
                case "/":
                    oper = new OperationDiv();
                    break;
            }
            return oper;
        }
    }
//Main
static void Main(string[] args)
        {
            Operation oper;
            oper = OperationFactory.createOprate("+");
            oper.NumberA = 1;
            oper.NumberB = 2;
            double result = oper.GetResult();

            Console.ReadKey();
        }