Need help with QFileSystemWatcher

[L.Marvell]

Qt 4.2.0-tp1, Linux, Windows

It seems I missed something but I can't get what.

What I do
In .h:

#include <QFileSystemWatcher>
...
QString destDir;
QFileSystemWatcher *watcher;
...

#include <QFileSystemWatcher>
...
QString destDir;
QFileSystemWatcher *watcher;
...

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In .cpp:

...
destDir = QFileDialog::getExistingDirectory( this, "Select directory", QFileDialog::ShowDirsOnly);
if (!destDir.isEmpty()){
	watcher->addPath(destDir);
}

...
destDir = QFileDialog::getExistingDirectory( this, "Select directory", QFileDialog::ShowDirsOnly);
if (!destDir.isEmpty()){
	watcher->addPath(destDir);
}

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There are also slot connected to watcher's signal directoryChanged(const QString&). When I tried to do something with selected dir (remove for example) nothing happened. So I've decided to check what is going on with the next addition code:

...
destDir = QFileDialog::getExistingDirectory( this, "Select directory", QFileDialog::ShowDirsOnly);
if (!destDir.isEmpty()){
	watcher->addPath(destDir);
	QString dirs;
	for(int i = 0; i < watcher->directories().count(); ++i){
		dirs.append(watcher->directories().at(i)).append("\n");
	}
	QMessageBoxEx::information(this, "debug", dirs);
}

...
destDir = QFileDialog::getExistingDirectory( this, "Select directory", QFileDialog::ShowDirsOnly);
if (!destDir.isEmpty()){
	watcher->addPath(destDir);
	QString dirs;
	for(int i = 0; i < watcher->directories().count(); ++i){
		dirs.append(watcher->directories().at(i)).append("\n");
	}
	QMessageBoxEx::information(this, "debug", dirs);
}

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And what I get
under Linux:

undefined reference to `QFileSystemWatcher::directories() const'

and under Windows:

undefined reference to `_imp___ZNK18QFileSystemWatcher11directoriesEv'