16.1.2. Abstract Factories and Libraries

16.1.2. Abstract Factories and Libraries
	16.1. Creational Patterns

[ fromfile: factory.xml id: componentfactory ]

Now consider two libraries, libdataobjects and libcustomer, each with its own (concrete) object factory, as shown in the UML diagram in Figure 16.1.

Figure 16.1. Libraries and factories

CustomerFactory, defined in Example 16.5, extends the functionality of ObjectFactory.

Example 16.5. src/libs/customer/customerfactory.h

[ . . . . ]
class CUSTOMER_EXPORT CustomerFactory : 
                             public QObject, public ObjectFactory {
  public:
    static CustomerFactory* instance();                      
    Customer* newCustomer(QString name, QObject* parent=0);  
    Address* newAddress(QString countryType = "USA", QObject* parent=0);
  private:
    CustomerFactory(QObject* parent=0);
};
[ . . . . ]

	Singleton factory method.
	Regular factory method, does not require a typecast.

CustomerFactory inherits the ability to create Address objects from ObjectFactory.
In addition, it knows how to create Customer objects.
The base-class newObject() method is smart enough to handle the classes added by Customer provided they are properly registered in that container.

Example 16.6. src/libs/customer/customerfactory.cpp

[ . . . . ]


CustomerFactory::CustomerFactory(QObject* parent) : QObject(parent) {
    m_knownClasses["Customer"] = Customer::staticMetaObject;
    m_knownClasses["CustomerList"] = Customer::staticMetaObject;
}


16.1.1. Abstract Factory		16.1.3. `qApp` and Singleton Pattern