设计模式-简单工厂模式

一个简单的计算器

1.首先写一个运算类Operation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;}
}

2.加减乘除类

class OperationAdd : Operation //加法类，继承运算类
{public override double GetResult(){double result = 0;result = NumberA + NumberB;return result;}
}
class OperationSub : Operation //减法类，继承运算类
{public override double GetResult(){double result = 0;result = NumberA - NumberB;return result;}
}
class OperationMul : Operation //乘法类，继承运算类
{public override double GetResult(){double result = 0;result = NumberA * NumberB;return result;}
}
class OperationDiv : Operation //除法类，继承运算类
{public override double GetResult(){double result = 0;if(NumberB == 0)throw new Exception("除数不能为0。");result = NumberA / NumberB;return result;}
}

3.简单工厂模式

public class OperationFactory
{public static Operation createOperate(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;}
}

客户端调用

Operation oper;
oper = OperationFactory.createOperate("+");
oper.NumberA = 1;
oper.NumberB = 2;
double result = oper.GetResult();

简单工厂模式的好处

1.之后要增加运算，只需要增加OperationXXX即可
2.之后要改某个运算，只需要修改OperationXXX即可