Qt之工厂模式（Factory Pattern）

工厂模式

QItemEditorFactory

class Q_GUI_EXPORT QItemEditorFactory
{
public:
	//按照type，创建对象，具体由创造器（QItemEditorCreatorBase）完成
    virtual QWidget *createEditor(QVariant::Type type, QWidget *parent) const;
	//向工厂注册具体对象的创造器
    void registerEditor(QVariant::Type type, QItemEditorCreatorBase *creator);
	//可以通过此接口获得设置默认工厂
    static const QItemEditorFactory *defaultFactory();
    static void setDefaultFactory(QItemEditorFactory *factory);
private:
    QHash creatorMap;
}；

QWidget *QItemEditorFactory::createEditor(QVariant::Type type, QWidget *parent) const
{
    QItemEditorCreatorBase *creator = creatorMap.value(type, 0);
    if (!creator) {
        const QItemEditorFactory *dfactory = defaultFactory();
        return dfactory == this ? 0 : dfactory->createEditor(type, parent);
    }
    return creator->createWidget(parent);
}

void QItemEditorFactory::registerEditor(QVariant::Type type, QItemEditorCreatorBase *creator)
{
    QHash::iterator it = creatorMap.find(type);
    if (it != creatorMap.end()) {
        QItemEditorCreatorBase *oldCreator = it.value();
        Q_ASSERT(oldCreator);
        creatorMap.erase(it);
        if (!creatorMap.values().contains(oldCreator))
            delete oldCreator; // if it is no more in use we can delete it
    }

    creatorMap[type] = creator;
}

const QItemEditorFactory *QItemEditorFactory::defaultFactory()
{
    static const QDefaultItemEditorFactory factory;
    if (q_default_factory)
        return q_default_factory;
    return &factory;
}

void QItemEditorFactory::setDefaultFactory(QItemEditorFactory *factory)
{
    static const QDefaultFactoryCleaner cleaner;
    delete q_default_factory;
    q_default_factory = factory;
}

QStyleFactory