Strange Error

**keeperofthegrove** · 17th October 2008, 17:05

Hello, I've been testing around, but I know have problem with this program -- it's giving me strange errors when Q_OBJECT is in the class:
the code
(i'm using Ubuntu, if it matters):

Qt Code:

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#include <QApplication>
#include <QPushButton>
#include <QWidget>
#include <QGridLayout>
#include <QString>
#include <QLineEdit>
#include <QVBoxLayout>
 
char* DigitAsString(int number)
{
      switch(number)
      {
		case 0: return "0";
		case 1: return "1";
		case 2: return "2";
		case 3: return "3";
		case 4: return "4";
		case 5: return "5";
		case 6: return "6";
		case 7: return "7";
		case 8: return "8";
		case 9: return "9";
		default: return "";
      }
}
class Calculator: public QWidget
{
Q_OBJECT	
 
public:
 
	Calculator(QWidget* parent = 0);
	void InitOperationButtons();
	void InitDigitButtons();
	void InitLineEdit();
	void LayoutButtons();
  	//Add(double, double);
  	//Divide(double, double);
 
public slots:
	void numberPressed()
	{
		editLine->setText(tr("1"));
	}
 
 
private:
	enum { NUM_KEYS = 12 };
	QPushButton *plusButton, *minusButton, *multipleButton, *divideButton;
	QPushButton *numberKeys[NUM_KEYS];	//Всички цифри като пушБутони
	QGridLayout *buttonsLayout;	//Разположението на бутоните
	QVBoxLayout *commonLayout;
	QLineEdit* editLine;
};
Calculator::Calculator(QWidget* parent)
: QWidget(parent)
{
 
	commonLayout = new QVBoxLayout;
	buttonsLayout = new QGridLayout;
	InitOperationButtons();
	InitDigitButtons();
	InitLineEdit();
	//
	LayoutButtons();
	commonLayout->addWidget(editLine);
	commonLayout->addLayout(buttonsLayout);
	//
	connect(numberKeys[0], SIGNAL(clicked()), this, SLOT(numberPressed()));
	//
	setWindowTitle(tr("Calculator"));	
	setLayout(commonLayout);
	setFixedSize(sizeHint());	//Най - добрата фиксирана позиция за елементите
}
void Calculator::InitOperationButtons()
{
	plusButton = new QPushButton(tr("+"), this);
	minusButton = new QPushButton(tr("-"), this);
	divideButton = new QPushButton(tr("/"), this);
	multipleButton = new QPushButton(tr("*"), this);
}
void Calculator::InitDigitButtons()
{
	for(int i = 0; i < NUM_KEYS; i++)
	{
	     if(i == 10)
	     { 
		  numberKeys[i] = new QPushButton(tr("."), this);
	     	  continue;
	     }
	     if(i == 11)
	     {
		  numberKeys[i] = new QPushButton(tr("="), this);
		  continue;
	     }
	     numberKeys[i] = new QPushButton(tr(DigitAsString(i)), this);
	     //Текста на бутоните ще бъде както следват цифрите
	}
}	
void Calculator::InitLineEdit()
{
	editLine = new QLineEdit;
	editLine->setMaxLength(15);	//Дължината на числото
}
void Calculator::LayoutButtons()
{
	buttonsLayout -> addWidget(plusButton, 0, 0);
	buttonsLayout -> addWidget(minusButton, 0, 1);
	buttonsLayout -> addWidget(divideButton, 0, 2);
	buttonsLayout -> addWidget(multipleButton, 0, 3);
	int row = 1;
	int col = 0;
	for(int i = 0; i < NUM_KEYS; i++, col++)
	{
	     if(i % 4 == 0)
	     {
		col = 0;
		buttonsLayout -> addWidget(numberKeys[i], ++row, col); 
	     }else
	     {
	     	buttonsLayout -> addWidget(numberKeys[i], row, col); 	
	     }	
	}
}
 
 
int main(int argc, char* argv[])
{
	QApplication qapp(argc, argv);
	Calculator* calculator = new Calculator();
	calculator -> show();
	return qapp.exec();
}

#include <QApplication>
#include <QPushButton>
#include <QWidget>
#include <QGridLayout>
#include <QString>
#include <QLineEdit>
#include <QVBoxLayout>

char* DigitAsString(int number)
{
      switch(number)
      {
		case 0: return "0";
		case 1: return "1";
		case 2: return "2";
		case 3: return "3";
		case 4: return "4";
		case 5: return "5";
		case 6: return "6";
		case 7: return "7";
		case 8: return "8";
		case 9: return "9";
		default: return "";
      }
}
class Calculator: public QWidget
{
Q_OBJECT	

public:
	
	Calculator(QWidget* parent = 0);
	void InitOperationButtons();
	void InitDigitButtons();
	void InitLineEdit();
	void LayoutButtons();
  	//Add(double, double);
  	//Divide(double, double);

public slots:
	void numberPressed()
	{
		editLine->setText(tr("1"));
	}

	
private:
	enum { NUM_KEYS = 12 };
	QPushButton *plusButton, *minusButton, *multipleButton, *divideButton;
	QPushButton *numberKeys[NUM_KEYS];	//Всички цифри като пушБутони
	QGridLayout *buttonsLayout;	//Разположението на бутоните
	QVBoxLayout *commonLayout;
	QLineEdit* editLine;
};
Calculator::Calculator(QWidget* parent)
: QWidget(parent)
{
	
	commonLayout = new QVBoxLayout;
	buttonsLayout = new QGridLayout;
	InitOperationButtons();
	InitDigitButtons();
	InitLineEdit();
	//
	LayoutButtons();
	commonLayout->addWidget(editLine);
	commonLayout->addLayout(buttonsLayout);
	//
	connect(numberKeys[0], SIGNAL(clicked()), this, SLOT(numberPressed()));
	//
	setWindowTitle(tr("Calculator"));	
	setLayout(commonLayout);
	setFixedSize(sizeHint());	//Най - добрата фиксирана позиция за елементите
}
void Calculator::InitOperationButtons()
{
	plusButton = new QPushButton(tr("+"), this);
	minusButton = new QPushButton(tr("-"), this);
	divideButton = new QPushButton(tr("/"), this);
	multipleButton = new QPushButton(tr("*"), this);
}
void Calculator::InitDigitButtons()
{
	for(int i = 0; i < NUM_KEYS; i++)
	{
	     if(i == 10)
	     { 
		  numberKeys[i] = new QPushButton(tr("."), this);
	     	  continue;
	     }
	     if(i == 11)
	     {
		  numberKeys[i] = new QPushButton(tr("="), this);
		  continue;
	     }
	     numberKeys[i] = new QPushButton(tr(DigitAsString(i)), this);
	     //Текста на бутоните ще бъде както следват цифрите
	}
}	
void Calculator::InitLineEdit()
{
	editLine = new QLineEdit;
	editLine->setMaxLength(15);	//Дължината на числото
}
void Calculator::LayoutButtons()
{
	buttonsLayout -> addWidget(plusButton, 0, 0);
	buttonsLayout -> addWidget(minusButton, 0, 1);
	buttonsLayout -> addWidget(divideButton, 0, 2);
	buttonsLayout -> addWidget(multipleButton, 0, 3);
	int row = 1;
	int col = 0;
	for(int i = 0; i < NUM_KEYS; i++, col++)
	{
	     if(i % 4 == 0)
	     {
		col = 0;
		buttonsLayout -> addWidget(numberKeys[i], ++row, col); 
	     }else
	     {
	     	buttonsLayout -> addWidget(numberKeys[i], row, col); 	
	     }	
	}
}

	
int main(int argc, char* argv[])
{
	QApplication qapp(argc, argv);
	Calculator* calculator = new Calculator();
	calculator -> show();
	return qapp.exec();
}

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And the errors:

Qt Code:

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kotg@kotg-laptop:~/programming/calculator/test$ make
g++ -Wl,--no-undefined -o test test2.o    -L/usr/lib -lQtGui -lQtCore -lpthread
test2.o: In function `Calculator::InitDigitButtons()':
test2.cpp:(.text+0x266): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x2e0): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x357): undefined reference to `Calculator::staticMetaObject'
test2.o: In function `Calculator::InitOperationButtons()':
test2.cpp:(.text+0x473): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x4cb): undefined reference to `Calculator::staticMetaObject'
test2.o:test2.cpp:(.text+0x523): more undefined references to `Calculator::staticMetaObject' follow
test2.o: In function `Calculator::Calculator(QWidget*)':
test2.cpp:(.text+0x6cb): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x6d2): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x7a8): undefined reference to `Calculator::staticMetaObject'
test2.o: In function `Calculator::Calculator(QWidget*)':
test2.cpp:(.text+0x87b): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x882): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x958): undefined reference to `Calculator::staticMetaObject'
collect2: ld returned 1 exit status
make: *** [test] Error 1

kotg@kotg-laptop:~/programming/calculator/test$ make
g++ -Wl,--no-undefined -o test test2.o    -L/usr/lib -lQtGui -lQtCore -lpthread
test2.o: In function `Calculator::InitDigitButtons()':
test2.cpp:(.text+0x266): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x2e0): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x357): undefined reference to `Calculator::staticMetaObject'
test2.o: In function `Calculator::InitOperationButtons()':
test2.cpp:(.text+0x473): undefined reference to `Calculator::staticMetaObject'
test2.cpp:(.text+0x4cb): undefined reference to `Calculator::staticMetaObject'
test2.o:test2.cpp:(.text+0x523): more undefined references to `Calculator::staticMetaObject' follow
test2.o: In function `Calculator::Calculator(QWidget*)':
test2.cpp:(.text+0x6cb): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x6d2): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x7a8): undefined reference to `Calculator::staticMetaObject'
test2.o: In function `Calculator::Calculator(QWidget*)':
test2.cpp:(.text+0x87b): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x882): undefined reference to `vtable for Calculator'
test2.cpp:(.text+0x958): undefined reference to `Calculator::staticMetaObject'
collect2: ld returned 1 exit status
make: *** [test] Error 1

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**keeperofthegrove** · 17th October 2008, 18:29

Alright, when I comment Q_OBJECT I can't use functional slots(which is right) and when I uncomment it, it shows me the same errors as above!

**lyuts** · 22nd October 2008, 13:57

Show me your makefile.

**lyuts** · 22nd October 2008, 14:01

I think this will be useful
http://doc.trolltech.com/4.4/moc.html#moc

**spirit** · 22nd October 2008, 14:16

offtop
you don't delete widget in this code

Qt Code:

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...
Calculator* calculator = new Calculator();
calculator -> show();
...

...
Calculator* calculator = new Calculator();
calculator -> show();
...

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create this widget in stack, i.e.

Qt Code:

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...
Calculator c;
c.show();
...

...
Calculator c;
c.show();
...

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or set attribute for this widget Qt::WA_DeleteOnClose
i.e.

Qt Code:

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...
Calculator* calculator = new Calculator();
calculator->setAttribute(Qt::WA_DeleteOnClose);
calculator -> show();
...

...
Calculator* calculator = new Calculator();
calculator->setAttribute(Qt::WA_DeleteOnClose);
calculator -> show();
...

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or delete this widget manually

Qt Code:

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...
Calculator* calculator = new Calculator();
calculator -> show();
...
bool res = app.exec();
delete calculator;
calculator = 0;
return res;

...
Calculator* calculator = new Calculator();
calculator -> show();
...
bool res = app.exec();
delete calculator;
calculator = 0;
return res;

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