设计模式-简单工厂模式

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