Error LNK2019: unresolved external symbol

Muhammad

I've been through 20 subject about this error, but I didn't figure how to fix it
-I'm using Qt 5.0.1, Qtcreatro 2.6.2 - with visual studio 2010 on windows 7 64bit
Here is my code
the .pro file
@#-------------------------------------------------

Project created by QtCreator 2013-02-02T23:22:32

#-------------------------------------------------

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = first
TEMPLATE = app
SOURCES += main.cpp
mycalculator.cpp
display.cpp

HEADERS += mycalculator.h
display.h

OTHER_FILES +=
Comments.txt
@

*The .h file *

@#ifndef MYCALCULATOR_H
#define MYCALCULATOR_H
#include <QPushButton>
#include <QTextEdit>
#include "display.h"
class MyCalculator : public QWidget
{
Q_OBJECT
public:
MyCalculator(QWidget *parent = 0);
//QSize sizeHint() const;
private:
Display *mydisplay;
enum{digitArrayIndex = 10};
QPushButton *digitButtons[digitArrayIndex];
QPushButton *addButton,*subButton,*mulButton,*divButton;
//there is 6 functions for now
QPushButton *sinButton,*cosButton,*tanButton;
QPushButton *powerButton,*sqrtButton,*lnButton;
QPushButton *equalButton,*pointButton,*clearButton,*delButton,*ansButton;
private slots:
void digitClicked();
void operationClicked();
void functionClicked();
void equalClicked();
void pointClicked();
void clearClicked();
void delClicked();
void ansClicked();
private: //functions
QPushButton *createButton(const QString &text, const char *buttonSlot);
};
#endif // MYCALCULATOR_H@

*The .cpp file *

@#include <QGridLayout>
#include <QScrollArea>
#include "mycalculator.h"
#include "display.h"
MyCalculator::MyCalculator(QWidget *parent)
: QWidget(parent)
{
QGridLayout *myBasicGrid = new QGridLayout(this);
myBasicGrid->setSizeConstraint(QLayout::SetFixedSize);
mydisplay = new Display;
//Implement operation buttons
addButton = createButton("+",SLOT(operationClicked()));
subButton = createButton("-",SLOT(operationClicked()));
mulButton = createButton("\303\227",SLOT(operationClicked()));
divButton = createButton("\303\267",SLOT(operationClicked()));
//Implement function buttons
sinButton = createButton("sin",SLOT(functionClicked()));
cosButton = createButton("cos",SLOT(functionClicked()));
tanButton = createButton("tan",SLOT(functionClicked()));
powerButton = createButton("x\302\262",SLOT(functionClicked()));
sqrtButton = createButton("\342\210\232",SLOT(functionClicked()));
lnButton = createButton("ln",SLOT(functionClicked()));
//The rest of the buttons
equalButton = createButton("=",SLOT(equalClicked()));
pointButton = createButton(".",SLOT(pointClicked()));
ansButton = createButton("Ans",SLOT(ansClicked()));
delButton = createButton("DEL",SLOT(delClicked()));
clearButton = createButton("AC",SLOT(clearClicked()));
//The digit buttons
digitButtons[0] = createButton("0",SLOT(digitClicked()));
for(int i = 1; i<digitArrayIndex; i++){
digitButtons[i] = createButton(QString::number(i),SLOT(digitClicked()));
int row = ((9 - i) / 3) + 2;
int column = ((i - 1) % 3);
myBasicGrid->addWidget(digitButtons[i],row,column); //Adding the digit buttons to the grid
}

//layout the display and the rest of the buttons
//myBasicGrid->addWidget(mydisplay,0,0,1,5);
myBasicGrid->addWidget(digitButtons[0],5,0);
myBasicGrid->addWidget(sinButton,1,0);
myBasicGrid->addWidget(cosButton,1,1);
myBasicGrid->addWidget(tanButton,1,2);
myBasicGrid->addWidget(powerButton,1,3);
myBasicGrid->addWidget(sqrtButton,1,4);
myBasicGrid->addWidget(delButton,2,3);
myBasicGrid->addWidget(clearButton,2,4);
myBasicGrid->addWidget(mulButton,3,3);
myBasicGrid->addWidget(divButton,3,4);
myBasicGrid->addWidget(addButton,4,3);
myBasicGrid->addWidget(subButton,4,4);
myBasicGrid->addWidget(pointButton,5,1);
myBasicGrid->addWidget(lnButton,5,2);
myBasicGrid->addWidget(ansButton,5,3);
myBasicGrid->addWidget(equalButton,5,4);

}

//Slots implemetation
void MyCalculator::digitClicked()
{
}
void MyCalculator::operationClicked()
{
}
void MyCalculator::functionClicked()
{
}
void MyCalculator::equalClicked()
{
}
void MyCalculator::pointClicked()
{
}

void MyCalculator::clearClicked()
{
}
void MyCalculator::delClicked()
{
}
void MyCalculator::ansClicked()
{
}
//functions implimintation
QPushButton *MyCalculator::createButton(const QString &text, const char *buttonSlot){
QPushButton *button = new QPushButton(text);
connect(button, SIGNAL(clicked()), this, buttonSlot);
return button;
}@

*and the display.h *file // another class I created and Inherited form QTextEdit
@#ifndef DISPLAY_H
#define DISPLAY_H

#include <QTextEdit>

class Display : public QTextEdit
{
Q_OBJECT
public:
explicit Display(QWidget *parent = 0);
};
#endif // DISPLAY_H@

*the display.cpp file *

@#include "display.h"

Display::Display(QWidget *parent) :
QTextEdit(parent)
{
}@

And here is the error

@ : error LNK2019: unresolved external symbol "public: __thiscall Display::Display(class QWidget *)" (??0Display@@QAE@PAVQWidget@@@Z) referenced in function "public: __thiscall MyCalculator::MyCalculator(class QWidget *)" (??0MyCalculator@@QAE@PAVQWidget@@@Z)
debug\first.exe : fatal error LNK1120: 1 unresolved externals
jom: C:\Users\FBM\Desktop\Calculator\first-build-Desktop_Qt_5_0_1_MSVC2010_32bit-debug\Makefile.Debug [debug\first.exe] Error 1120@
When I comment the code in line 13 of the .cpp file the program works fine.
Any help plz

francescmm

You should include QFont:

@#include <QFont>@

In addition, in the .cpp file I cannot see when you create the "display" object:

@//display->setReadOnly(true);
/QFont displayFont = display->font();
displayFont.setPointSize(displayFont.pointSize() + 4);
display->setFont(displayFont);/
//Implement operation buttons@

Muhammad

Forget about the font and all of these stuff they are commented ,any way I edited the post and deleted them.
The creation of the Display object is in line 10

b1gsnak3

Well... I don't see the #include <QWidget> anywhere in your headers

goblincoding

[quote author="b1gsnak3" date="1360246401"]Well... I don't see the #include <QWidget> anywhere in your headers[/quote]

This won't be required as it's part of the inheritance chain.

francescmm

I have tried to compile your program and it runs well for me. May be you could re-generate the Makefile and then clean project and re-compile again?

When I had these problems I had some methods declared but not implemented. Can ensure yourself that all the code posted is that you have?

We will solve this issue!

Jeroentjehome

What usually works for me is to through away the entire build directory that Qt creates when debugging or running a program. This will remove all files generated by QMake (also your ui files). Then rebuild the program. Problem might be fixed then.
greetz

Muhammad

Yes Thanks guys It did work after deleting the build folder, restart and rebuild :).

utcenter

I often get such errors, 99.99% of the time it is solved by clicking "clean all" then "run qmake" then "rebuild all".

inejose

[quote author="utcenter" date="1360368863"]I often get such errors, 99.99% of the time it is solved by clicking "clean all" then "run qmake" then "rebuild all".[/quote]

The 0.01% remaining could be missing the name space in the .cpp file. For example:

You define a function in your class header (MyClass.h) :

@ int myFunction(int a, int b);@

But in the MyClass.cpp you miss the namespace:

@int myFunction(int a, int b){
// ...
}@

instead of

@int Class::myFunction(int a, int b){
// ...
}@

When calling that "myFunction" in your code, the error appears.

QtSurfer

Worked for me on a project getting this error code :
[quote author="utcenter" date="1360368863"]I often get such errors, 99.99% of the time it is solved by clicking "clean all" then "run qmake" then "rebuild all".[/quote]

Sir, you rock

QtSurfer

Worked for me on a project getting this error code :
[quote author="utcenter" date="1360368863"]I often get such errors, 99.99% of the time it is solved by clicking "clean all" then "run qmake" then "rebuild all".[/quote]

Sir, you rock