自由意志

黑人夏川

简单工厂模式

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优势

  1. 一个调用者想创建一个对象，只要知道其名称就可以了;
  2. 扩展性高，如果想增加一个产品，只要扩展一个工厂类就可以;
  3. 屏蔽产品的具体实现，调用者只关心产品的接口。
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class Factory
{
public:
    Factory() {}
    virtual ~Factory() { std::cout << "~Factory" << std::endl; }
    // This virtual is very important
    // If you don't have this virtual, try this code
    // Factory *f = new ComputerFactory;
    // delete f;
    // ComputerFactory's destructor will not be called, causing a memory leak

    virtual void name() { std::cout << "Factory" << std::endl; }
};
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class ComputerFactory : public Factory
{
public:
    ComputerFactory()
        : Factory()
    {}
    virtual ~ComputerFactory() { std::cout << "~ComputerFactory" << std::endl; }

    virtual void name() { std::cout << "ComputerFactory" << std::endl; }
};

class PhoneFactory : public Factory
{
public:
    PhoneFactory()
        : Factory()
    {}
    virtual ~PhoneFactory() { std::cout << "~PhoneFactory" << std::endl; }

    virtual void name() { std::cout << "PhoneFactory" << std::endl; }
};

创建工厂的方法

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enum FactoryType { Computer, Phone };

Factory *createFactory(FactoryType type)
{
    switch (type) {
    case Computer: return new ComputerFactory;
    case Phone: return new PhoneFactory;
    default: break;
    }
    return new Factory;
}

测试

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int main(int argc, char *argv[])
{
    std::unique_ptr<Factory> f(createFactory(FactoryType::Computer));
    std::unique_ptr<Factory> f1(createFactory(FactoryType::Phone));
    std::unique_ptr<Factory> f2(createFactory(FactoryType(-1)));

    return 0;
}

结果

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~Factory
~PhoneFactory   
~Factory        
~ComputerFactory
~Factory

Factory源码