设计模式-工厂方法模式

设计模式-工厂方法模式

工厂方法模式实现计算器

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;
    }
}
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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;
    }
}
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先创建一个工厂接口

interface IFactory
{
    Operation CreateOperation();
}
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具体工厂实现这个接口

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();
    }
}
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客户端实现

IFactory operFactory = new AddFactory();
Operation oper = operFactory.CreateOperation();
oper.NumberA = 1;
oper.NumberB = 2;
double result = oper.GetResult();
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简单工厂模式与工厂方法模式的比较

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相关的类，对于客户端来说，去除了与具体产品的依赖。

工厂方法模式，定义了一个用于创建对象的接口，让子类决定实例化哪一个类。工厂方法使一个类的实例化延迟到其子类。