How to instantiate a class if I dont know its name?

[anoraxis]

Hi:

The application I'm trying to develop must be extended using plugins. I have a XML file similar to this (I omitted some non important parts):

<program>
<component type="plugin1"/>
<component type="plugin2"/>
<component type="plugin1"/>
<component type="plugin3"/>
</program>

So, for each <component> element that I read I create a new page on a QStackedWidget containing a custom widget defined by the classes Plugin1, Plugin2 and Plugin3. Is very easy when I know the names of all the plugins because I can do something like:

class AbstractPlugin : public QObject{
  //...
  virtual QWidget* widget() = 0;
};
 
//all these classes implements "widget()"
class Plugin1 : public AbstractPlugin{/*...*/};
class Plugin2 : public AbstractPlugin{/*...*/};
class Plugin3 : public AbstractPlugin{/*...*/};
 
QList<AbstractPlugin* > components
QString type //this value was readed from the XML in some moment
 
if(type == "Plugin1")
  components.append(new Plugin1());
else if(type == "Plugin2")
  components.append(new Plugin2());
else if(type == "Plugin3")
  components.append(new Plugin3());
 
foreach(AbstractPlugin* c, components){
    stackedWidget->addPage(c->widget());
}

class AbstractPlugin : public QObject{
  //...
  virtual QWidget* widget() = 0;
};

//all these classes implements "widget()"
class Plugin1 : public AbstractPlugin{/*...*/};
class Plugin2 : public AbstractPlugin{/*...*/};
class Plugin3 : public AbstractPlugin{/*...*/};

QList<AbstractPlugin* > components
QString type //this value was readed from the XML in some moment

if(type == "Plugin1")
  components.append(new Plugin1());
else if(type == "Plugin2")
  components.append(new Plugin2());
else if(type == "Plugin3")
  components.append(new Plugin3());

foreach(AbstractPlugin* c, components){
    stackedWidget->addPage(c->widget());
}

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But, if I dont know the names of all the plugins because I don't write each one, how can I specify the correct constructor to call?