工厂方法模式

//工厂方法模式(创建型)

//与简单工厂模式的区别：
//简单工厂模式的最大优点在于工厂类中包含了必要的逻辑判断，根据客户端的选择条件动态实例化的类，对于客户端来说，
//去除了与具体产品的依赖。但是问题也在这里，就像为如果为简单工厂模式下的二元四则运算添加一个新的功能，如计算
// ”M的N次方“，这时候我们就需要在工厂类中增加一个case分支，这就违背了开闭原则。而工厂方法模式想要增加这个功能
//时，类都是在增加，没有修改，但客户端需要进行相应的修改。

//1、工厂方法模式下的二元四则运算

 

// 二元运算的基类
public class Operation
{
    //私有成员
    private double _numberA = 0;
private double _numberB = 0;
//公共属性
public double NumberA
{
    get { return _numberA;}
set { _numberA = value;}
}
public double NumberB
{
    get { return _numberB; }
set { _numberB = value; }
}
//虚函数
public virtual double GetResult()
{
    double result = 0;
return result;
}
}
// 四则运算类
class OperationAdd : Operation
{
    //重写基类的虚函数
    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)
{
    result = NumberA / NumberB;
}
else
{
    throw new Exception("can't divided by 0");
}
return result;
}
}
//工厂接口
interface IFactory
{
Operation CreateOperation();
}
//加减乘除各创建一个具体工厂实现接口
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();
}
}
public class test
{
public static void Main()
{
IFactory operFactory = new AddFactory(); // 这个位置可更改
Operation oper = operFactory.CreateOperation();
oper.NumberA = 1;
oper.NumberB = 2;
double result = oper.GetResult();
Console.WriteLine(result);
Console.ReadLine();
}
}