Problem with slot

[stefek]

Thanks, this problem is solved, but now come other problems.

calc.h:18: error: ISO C++ forbids declaration of ‘QLCDNumber’ with no type
calc.h:18: error: expected ‘;’ before ‘*’ token

So I added the declaration of QLCDNumber class: class QLCDNumber;. and now are problems with the inside of the slot:

calc.cpp:17: error: invalid use of member (did you forget the ‘&’ ?)

How can I solve it?

I think i solve this problem. I add to class Calc new variable int value, which stores the actual result of calculations and use display function.

But... I have new problem...
Here is my source code:

//calc.h
 
#ifndef CALC_H
#define CALC_H
 
#include <QtGui/QDialog>
 
class QLCDNumber;
namespace Ui
{
    class Calc;
}
 
class Calc : public QDialog
{
    Q_OBJECT
 
     private:
          QLCDNumber *lcdNumber;
          QPushButton *seventhButton;
          QPushButton *eighthButton;
          QPushButton *ninethButton;
          QPushButton *divisionButton;
          QPushButton *fourthButton;
          QPushButton *fifthButton;
          QPushButton *sixthButton;
          QPushButton *additionButton;
          QPushButton *firstButton;
          QPushButton *secondButton;
          QPushButton *thirdButton;
          QPushButton *subtractionButton;
          QPushButton *zeroButton;
          QPushButton *sqrtButton;
          QPushButton *multiplicationButton;
          QPushButton *moduloButton;
          int value;
 
public:
    Calc(QWidget *parent = 0);
    ~Calc();
 
    public slots:
          void setVal(const int &val);
 
 
 
private:
    Ui::Calc *ui;
};
 
#endif // CALC_H

//calc.h

#ifndef CALC_H
#define CALC_H

#include <QtGui/QDialog>

class QLCDNumber;
namespace Ui
{
    class Calc;
}

class Calc : public QDialog
{
    Q_OBJECT

     private:
          QLCDNumber *lcdNumber;
          QPushButton *seventhButton;
          QPushButton *eighthButton;
          QPushButton *ninethButton;
          QPushButton *divisionButton;
          QPushButton *fourthButton;
          QPushButton *fifthButton;
          QPushButton *sixthButton;
          QPushButton *additionButton;
          QPushButton *firstButton;
          QPushButton *secondButton;
          QPushButton *thirdButton;
          QPushButton *subtractionButton;
          QPushButton *zeroButton;
          QPushButton *sqrtButton;
          QPushButton *multiplicationButton;
          QPushButton *moduloButton;
          int value;

public:
    Calc(QWidget *parent = 0);
    ~Calc();

    public slots:
          void setVal(const int &val);



private:
    Ui::Calc *ui;
};

#endif // CALC_H

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#include "calc.h"
#include "ui_calc.h"
 
Calc::Calc(QWidget *parent)
    : QDialog(parent), ui(new Ui::Calc)
{
    ui->setupUi(this);
    connect(zeroButton, SIGNAL(clicked()), this, SLOT(setVal(0)));
}
 
Calc::~Calc()
{
    delete ui;
}
 
void Calc::setVal(const int &val){
 
    value*=10;
    value+=val;
    lcdNumber ->display(value);
}

#include "calc.h"
#include "ui_calc.h"

Calc::Calc(QWidget *parent)
    : QDialog(parent), ui(new Ui::Calc)
{
    ui->setupUi(this);
    connect(zeroButton, SIGNAL(clicked()), this, SLOT(setVal(0)));
}

Calc::~Calc()
{
    delete ui;
}

void Calc::setVal(const int &val){

    value*=10;
    value+=val;
    lcdNumber ->display(value);
}

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In the constructor I add the conection between zero button and LCDNumber. It should works, but in the console are errors:

Segmentation fault

I have no idea how to do this. Could anyone help me?
It's harder than I thought at the beginning of lessons.

I've read in documentation that the signal and slot parameters mustn't contain variable name, but only type, so how can I send the value, which is needed?