Link error while compiling qt example on visual studio

Question

I have a problem in compiling a qt example from c++ GUI programming with qt 4 second edition book on visual c++ express 2010.Since qt visual studio add-in doesn't work with express edition , I configured it by myself by just adding library dependencies: qtmaind.lib QtCored4.lib QtGuid4.lib .Also I can compile a sample code 'Hello,Qt!' without error. My project contains two .cpp files and a header file:
findDialog.h:

#ifndef FINDDIALOG_H
#define FINDDIALOG_H

#include <QtGui\qdialog.h>
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;

class findDialog : public QDialog
{
    Q_OBJECT
public:
    findDialog(QWidget* parent = 0);
signals:
    void findNext(const QString &str , Qt::CaseSensitivity cs);
    void findPrevious(const QString &str , Qt::CaseSensitivity cs);
private slots:
    void findClicked();
    void enableFindButton(const QString& text);
private:
    QLabel* label;
    QLineEdit* lineEdit;
    QCheckBox* caseCheckBox;
    QCheckBox* backwardCheckBox;
    QPushButton* findButton;
    QPushButton* closeButton;
};
#endif

findDialog.cpp:

#include <QtGui\QtGui>
#include "findDialog.h"


findDialog::findDialog(QWidget* parent) : QDialog(parent)
{
    label = new QLabel(tr("Find &what:"));
    lineEdit = new QLineEdit;
    label->setBuddy(lineEdit);

    caseCheckBox = new QCheckBox(tr("Match &case"));
    backwardCheckBox = new QCheckBox(tr("Search &backward"));

    findButton = new QPushButton(tr("&Find"));
    findButton->setDefault(true);
    findButton->setEnabled(false);

    closeButton = new QPushButton(tr("Close"));

    connect(lineEdit , SIGNAL(textChanged(const QString&)) , this , SLOT(enableFindButton(const QString&)));
    connect(findButton , SIGNAL(clicked()) , this , SLOT(findClicked()));
    connect(closeButton , SIGNAL(clicked()) , this , SLOT(close()));

    QHBoxLayout* topLeftLayout = new QHBoxLayout;
    topLeftLayout->addWidget(label);
    topLeftLayout->addWidget(lineEdit);

    QVBoxLayout *leftLayout = new QVBoxLayout;
    leftLayout->addLayout(topLeftLayout);
    leftLayout->addWidget(caseCheckBox);
    leftLayout->addWidget(backwardCheckBox);

    QVBoxLayout *rightLayout = new QVBoxLayout;
    rightLayout->addWidget(findButton);
    rightLayout->addWidget(closeButton);
    rightLayout->addStretch();

    QHBoxLayout *mainLayout = new QHBoxLayout;
    mainLayout->addLayout(leftLayout);
    mainLayout->addLayout(rightLayout);
    setLayout(mainLayout);

    setWindowTitle(tr("Find"));
    setFixedHeight(sizeHint().height());
}

void findDialog::findClicked()
{
    QString text = lineEdit->text();
    Qt::CaseSensitivity cs = caseCheckBox->isChecked() ? Qt::CaseSensitive : Qt::CaseInsensitive;

    if(backwardCheckBox->isChecked())
        emit findPrevious(text , cs);
    else
        emit findNext(text , cs);
}

void findDialog::enableFindButton(const QString& text)
{
    findButton->setEnabled(!text.isEmpty());
}

main.cpp:

#include <QtGui\qapplication.h>
#include <iostream>
#include "findDialog.h"



int main(int argc , char* argv[])
{
    QApplication app(argc , argv);
    findDialog* dialog = new findDialog;
    dialog->show();
    return app.exec();
}

When I compile this project , I get 6 link errors :

LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall findDialog::metaObject(void)const " (?metaObject@findDialog@@UBEPBUQMetaObject@@XZ)

LNK2001: unresolved external symbol "public: virtual void * __thiscall findDialog::qt_metacast(char const *)" (?qt_metacast@findDialog@@UAEPAXPBD@Z)

LNK2001: unresolved external symbol "public: virtual int __thiscall findDialog::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@findDialog@@UAEHW4Call@QMetaObject@@HPAPAX@Z)

LNK2001: unresolved external symbol "public: static struct QMetaObject const findDialog::staticMetaObject" (?staticMetaObject@findDialog@@2UQMetaObject@@B)

LNK2019: unresolved external symbol "protected: void __thiscall findDialog::findNext(class QString const &,enum Qt::CaseSensitivity)" (?findNext@findDialog@@IAEXABVQString@@W4CaseSensitivity@Qt@@@Z) referenced in function "private: void __thiscall findDialog::findClicked(void)" (?findClicked@findDialog@@AAEXXZ)

LNK2019: unresolved external symbol "protected: void __thiscall findDialog::findPrevious(class QString const &,enum Qt::CaseSensitivity)" (?findPrevious@findDialog@@IAEXABVQString@@W4CaseSensitivity@Qt@@@Z) referenced in function "private: void __thiscall findDialog::findClicked(void)" (?findClicked@findDialog@@AAEXXZ)

Thank you in advance and sorry for my bad english.

Ekkehard.Horner Ekkehard.Horner · Accepted Answer · 2012-01-03T19:13:18

Perhaps you can solve your problem with a lot of work based on Kia.celever's diagnosis and further info from

But all this work won't further your knowledge/skills wrt programming in general, c++, or qt. If Visual Studio is important for you, invest in an unrestricted version for professional use and install the add-in and avoid the hassle of configuring a tool for a use it is not meant for. Otherwise, install QT-Creator (see (2); Qt Creator IDE and tools).

Link error while compiling qt example on visual studio

4 Answers