工厂方法模式 = 简单工厂模式 + 开闭原则
类的个数成倍增多，维护成本很高
适用场景：
- 客户端不知道它所需要的对象的类
- 抽象工厂类通过其子类来指定创建哪个对象
// 工厂方法模式
class AbstractFruit{
public:
virtual void showName() = 0;
};
class Apple : public AbstractFruit{
public:
void showName() override{
cout << "我是苹果！" << endl;
}
};
class Banana : public AbstractFruit{
public:
void showName() override{
cout << "我是香蕉！" << endl;
}
};
class Pear : public AbstractFruit{
public:
void showName() override{
cout << "我是鸭梨！" << endl;
}
};
// 抽象工厂
class AbstractFruitFactory{
public:
virtual AbstractFruit* CreateFruit() = 0;
};
class AppleFactory : public AbstractFruitFactory{
public:
AbstractFruit* CreateFruit() override{
return new Apple;
}
};
class PearFactory : public AbstractFruitFactory{
public:
AbstractFruit* CreateFruit() override{
return new Pear;
}
};
class BananaFactory : public AbstractFruitFactory{
public:
AbstractFruit* CreateFruit() override{
return new Banana;
}
};
int main()
{
AbstractFruitFactory* factory = nullptr;
AbstractFruit* fruit = nullptr;
factory = new AppleFactory;
fruit = factory->CreateFruit();
fruit->showName();
delete fruit;
delete factory;
factory = new BananaFactory;
fruit = factory->CreateFruit();
fruit->showName();
delete fruit;
delete factory;
factory = new PearFactory;
fruit = factory->CreateFruit();
fruit->showName();
delete fruit;
delete factory;
return 0;
}