Combining two projects in one

[Bazelboday]

Hello! What do we have : 1 working project , it's just a QWidget with number of buttons, and second one is another project,also using QWidget with some buttons. Both dialogs were edited in UIDesigner,and works separately.
What i want : to evoke 1 dialog from another.
How i combined projects: just added code using addExistingFile, then add .h,.cpp. and .ui files into one project.
when i compile this project now i get errors like this :

smtp.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) class QDebug __cdecl operator<<(class QDebug,enum QAbstractSocket::SocketError)" (_imp??6@YA?AVQDebug@@V0@W4SocketError@QAbstractSocket@@@Z) referenced in function "private: void __cdecl Smtp::errorReceived(enum QAbstractSocket::SocketError)" (?errorReceived@Smtp@@AEAAXW4SocketError@QAbstractSocket@@@Z)
smtp.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) public: virtual __cdecl QSslSocket::~QSslSocket(void)" (_imp??1QSslSocket@@UEAA@XZ) referenced in function "public: virtual void * __cdecl QSslSocket::`scalar deleting destructor'(unsigned int)" (??_GQSslSocket@@UEAAPEAXI@Z)
smtp.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) public: void __cdecl QSslSocket::connectToHostEncrypted(class QString const &,unsigned short,class QFlags<enum QIODevice::OpenModeFlag>,enum QAbstractSocket::NetworkLayerProtocol)" (_imp?connectToHostEncrypted@QSslSocket@@QEAAXAEBVQString@@GV?$QFlags@W4OpenModeFlag@QIODevice@@@@W4NetworkLayerProtocol@QAbstractSocket@@@Z) referenced in function "public: void __cdecl Smtp::sendMail(class QString const &,class QString const &,class QString const &,class QString const &,class QStringList)" (?sendMail@Smtp@@QEAAXAEBVQString@@000VQStringList@@@Z)

What is the problem, any help is highly appreciated! Thanks in advance!

[jsulm]

Do you have QT += network in your PRO file?

[Bazelboday]

yes, now i just have 2 errors, the following code makes error :
MsgSender w(this) ;

browser.obj:-1: error: LNK2019: unresolved external symbol "public: __cdecl MsgSender::MsgSender(class QWidget *)" (??0MsgSender@@QEAA@PEAVQWidget@@@Z) referenced in function "public: void __cdecl Browser::showTable(class QString const &)" (?showTable@Browser@@QEAAXAEBVQString@@@Z)
browser.obj:-1: error: LNK2019: unresolved external symbol "public: virtual __cdecl MsgSender::~MsgSender(void)" (??1MsgSender@@UEAA@XZ) referenced in function "public: void __cdecl Browser::showTable(class QString const &)" (?showTable@Browser@@QEAAXAEBVQString@@@Z)

[jsulm]

What is MsgSender? Where is it defined? I think you forgot to add it to your project.

[Bazelboday]

solved! i've deleted release folder and rebuilded project, because qt didn't generated my ui form.