Qt动态重生类厂

class QConstructHelper
{
public:
    virtual void * create() = 0;
};
template<typename T>
class QMetaTypeConstructHelper : public QConstructHelper
{
public:
    QMetaTypeConstructHelper(){}
    void * create(){return new T;}
};
template<typename T>
int qRegisterConstructHelper(const char *name)
{
    return qRegisterMetaType< QMetaTypeConstructHelper<T> >(name);
}
void * qConstructHelper(const char* name);
QObject * qObjectConstructHelper( const char* name );
//关键函数的实现
void * qConstructHelper(const char* name)
{
    int id = QMetaType::type( name );
    if (id != QMetaType::UnknownType)
    {
        QConstructHelper * creator = static_cast<QConstructHelper*>(QMetaType::create( id ));
        if(creator)
        {
            void * p = creator->create();
            QMetaType::destroy(id,creator);
            return p;
        }
    }
    return NULL;
}

QObject * qObjectConstructHelper( const char* name )
{
    return  static_cast<QObject*>(qConstructHelper(name));
}
用法示例：
    qRegisterConstructHelper<Data>("myData");
    qRegisterConstructHelper<Widget>("widget");
    Widget * w = qobject_cast<Widget*>(qObjectConstructHelper("widget"));
    if(w)
    {
        w->show();
        return a.exec();
    }
另外这个函数可以创建Qt的原生对象（除窗体对象已外的）
void * qMetaTypeCreate(const char *name)
{
    int id = QMetaType::type( name );
    if (id != QMetaType::UnknownType)
    {
        return QMetaType::create( id );
    }
    return NULL;
}