第五章 Caché 设计模式 工厂方法

工厂方法模式实现，客户端需要决定实例化哪一个工厂来实现运算类，选择判断的问题还是存在的，也就是说，工厂方法把简单工厂的内部逻辑判断移到了客户端来进行，你想加功能，本来是改工厂类，现在是修改客户端。

完整示例

结构图

image.png

抽象对象类

Class PHA.YX.Design.Factory.Computer Extends %RegisteredObject
{

Method Create() [ Abstract ]
{
}

Method Install() [ Abstract ]
{
}

}

实例对象类

Class PHA.YX.Design.Factory.HPComputer Extends Computer
{

Method Create()
{
    w "创建了HP电脑",!
}

Method Install()
{
    w "安装了HP电脑",!
}

}

Class PHA.YX.Design.Factory.LenovoComputer Extends Computer
{

Method Create()
{
    w "创建了Lenovo电脑",!
}

Method Install()
{
    w "安装了Lenovo电脑",!
}

}

抽象工厂类

Class PHA.YX.Design.Factory.IFactory [ Abstract ]
{

ClassMethod CreateComputer() As Computer [ Abstract ]
{
}

}

实例工厂类

Class PHA.YX.Design.Factory.HPFactory Extends (%RegisteredObject, IFactory)
{

ClassMethod CreateComputer() As Computer
{
    q ##class(HPComputer).%New()
}

}

Class PHA.YX.Design.Factory.LenovoFactory Extends (%RegisteredObject, IFactory)
{

ClassMethod CreateComputer() As Computer
{
    q ##class(LenovoComputer).%New()
}

}

调用

/// d ##class(PHA.YX.Design.Program).Factory() 
ClassMethod Factory()
{
    #dim factory as PHA.YX.Design.Factory.IFactory
    s factory = ##class(PHA.YX.Design.Factory.HPFactory).%New()
    #dim hpComputer as PHA.YX.Design.Factory.Computer
    s hpComputer = factory.CreateComputer()
    d hpComputer.Create()
    d hpComputer.Install()
    
    
    s factory = ##class(PHA.YX.Design.Factory.LenovoFactory).%New()
    #dim lenovoComputer as PHA.YX.Design.Factory.Computer
    s lenovoComputer = factory.CreateComputer()
    d lenovoComputer.Create()
    d lenovoComputer.Install()
}

DHC-APP> d ##class(PHA.YX.Design.Program).Factory()
创建了HP电脑
安装了HP电脑
创建了Lenovo电脑
安装了Lenovo电脑

思考

用第一章的计算案例，来改写成工厂模式。感兴趣的同学实现后可以发我一起参考下。