Help me with QNetworkAccessManager. Err: undefined reference.

Im going to write a small program to download a link (QUrl) using QNetworkAccessManager. I found in QT help things are explain very simple. I do the same:
in Header file MainWindow.h:

Code:

---

QNetworkAccessManager *manager;

---

in MainWindow.cpp:

Code:

---

manager = new QNetworkAccessManager(this);
QNetworkReply *rep = manager->get(QNetworkRequest(QUrl("http://www.google.com")));

---

But when I compile this prog, there are error messages: undefined reference to QNetworkAccessManager::QNetworkAccessManager(QObje ct*)

I cant understand why even though I read help file for ten times. Please help me. Thank you very mcuh.

You must have Qt+= network in .pro file

thank you very much. Its allright now.

For future reference, the necessary additions to the project file for any class are found on the page describing the module containing the class:
http://doc.qt.nokia.com/latest/qtnetwork.html