Connect signal to slot from different class

[Leutzig]

Hi,

I have a signal that I want to connect to a slot found in a different class. How do I do that?
What I thought I could do:

Class A header:

#include "classB.h"
 
class ClassA
{
 
Q_Object
 
public:
ClassA();
...
...
 
signals:
void stuffChange( const QString & );
 
private:
 
ClassB classb
};

#include "classB.h"

class ClassA
{

Q_Object

public:
ClassA();
...
...

signals:
void stuffChange( const QString & );

private:

ClassB classb
};

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And in Class A constructor:

connect(this, SIGNAL( stuffChange( const QString & ) ), &classb, SLOT( setStuff( const QString & ) ) );

connect(this, SIGNAL( stuffChange( const QString & ) ), &classb, SLOT( setStuff( const QString & ) ) );

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Class B header:

class ClassB
{
 
Q_Object
 
public:
ClassB();
...
...
 
public slots:
void setStuff( const QString & );
 
private:
QString stuff;
 
};

class ClassB
{

Q_Object

public:
ClassB();
...
...

public slots:
void setStuff( const QString & );

private:
QString stuff;

};

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This gives me the error: LNK2019: unresolved external symbol "public: __ ...
What is the right way to do this?

[anda_skoa]

The connect looks ok.
Are both ClassA and ClassB derived from QObject?

Cheers,
_

[Leutzig]

Both classes look like this in the header (which was written by Qt when the project was made):

classA : public QWidget
{
    Q_OBJECT
 
public:
...

classA : public QWidget
{
    Q_OBJECT

public:
...

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classB : public QWidget
{
    Q_OBJECT
 
public:
...

classB : public QWidget
{
    Q_OBJECT

public:
...

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I'm not sure if that means that they are derived from Q_OBJECT.

[Vikram.Saralaya]

It looks fine. If you added Q_OBJECT later then you might want to try running qmake again.

May be showing a bit more of the actual code might be a better way to get more help..

[Leutzig]

I've tried running qmake many times and deleting build directory, Clean All, made a new project and inserted every class and function individually, but when I add the object of the other class and use it in the connect, I get that error.
The actual classes are these:

ColorSelect header (ClassA):

#ifndef COLORSELECT_H
#define COLORSELECT_H
 
#include "device.h"
#include "serialcom.h"
 
namespace Ui {
class ColorSelect;
}
 
class ColorSelect : public QWidget
{
    Q_OBJECT
    //Q_PROPERTY(QColor color READ color NOTIFY colorChanged)
 
public:
    explicit ColorSelect(QWidget *parent = 0, SerialCom *cS = NULL);
    QWidget * getColorWheelWidgetPtr() const;
    QColor getRGBColor() const;
    void setItemData(QString, QString);
    ~ColorSelect();
 
signals:
    void colorChanged(QColor arg);
    void houseChange(const QString &);
    void unitChange(const QString &);
 
private slots:
    void updatePalette( const QColor & );
    void on_HouseAndUnitChanged( const QString & house, const QString & unit );
    void on_ColorChanged();
    void on_upButton_clicked();
    void on_downButton_clicked();
    void on_addDeviceButton_clicked();
    void on_deleteDeviceButton_clicked();
    void on_listWidget_itemDoubleClicked(QListWidgetItem *item);
    void on_chooseButton_clicked();
 
private:
    Ui::ColorSelect *ui;
    QColor rgbColor;
    SerialCom *serialCom;
    Device device;
};
 
#endif // COLORSELECT_H

#ifndef COLORSELECT_H
#define COLORSELECT_H

#include "device.h"
#include "serialcom.h"

namespace Ui {
class ColorSelect;
}

class ColorSelect : public QWidget
{
    Q_OBJECT
    //Q_PROPERTY(QColor color READ color NOTIFY colorChanged)

public:
    explicit ColorSelect(QWidget *parent = 0, SerialCom *cS = NULL);
    QWidget * getColorWheelWidgetPtr() const;
    QColor getRGBColor() const;
    void setItemData(QString, QString);
    ~ColorSelect();

signals:
    void colorChanged(QColor arg);
    void houseChange(const QString &);
    void unitChange(const QString &);

private slots:
    void updatePalette( const QColor & );
    void on_HouseAndUnitChanged( const QString & house, const QString & unit );
    void on_ColorChanged();
    void on_upButton_clicked();
    void on_downButton_clicked();
    void on_addDeviceButton_clicked();
    void on_deleteDeviceButton_clicked();
    void on_listWidget_itemDoubleClicked(QListWidgetItem *item);
    void on_chooseButton_clicked();

private:
    Ui::ColorSelect *ui;
    QColor rgbColor;
    SerialCom *serialCom;
    Device device;
};

#endif // COLORSELECT_H

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ColorSelect constructor from ColorSelect cpp:

#include "colorselect.h"
#include "ui_colorselect.h"
#include "devicedialog.h"
#include <qdebug.h>
 
ColorSelect::ColorSelect(QWidget *parent, SerialCom *serialCom) : QWidget(parent),
    ui(new Ui::ColorSelect)
{
    ui->setupUi(this);
    connect(ui->redSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    connect(ui->greenSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    connect(ui->blueSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    ui->redLine->setReadOnly(true);
    ui->greenLine->setReadOnly(true);
    ui->blueLine->setReadOnly(true);
    on_ColorChanged();
    this->serialCom = serialCom;
 
    // highlights default device
    ui->listWidget->item(0)->setSelected(true);
    ui->listWidget->setCurrentItem(ui->listWidget->item(0));
 
    // sets default values for default device
    ui->listWidget->item(0)->setData(Qt::UserRole, "A01");
 
    connect( ui->colorWheelWidget, SIGNAL( colorChange( const QColor & ) ), this, SLOT( updatePalette( const QColor & ) ) );
    connect(this, SIGNAL( houseChange( const QString & ) ), &device, SLOT( setHouse( const QString & ) ) );
    connect(this, SIGNAL( unitChange( const QString & ) ), &device, SLOT( setUnit( const QString & ) ) );
}

#include "colorselect.h"
#include "ui_colorselect.h"
#include "devicedialog.h"
#include <qdebug.h>

ColorSelect::ColorSelect(QWidget *parent, SerialCom *serialCom) : QWidget(parent),
    ui(new Ui::ColorSelect)
{
    ui->setupUi(this);
    connect(ui->redSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    connect(ui->greenSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    connect(ui->blueSlider, SIGNAL(sliderReleased()), SLOT(on_ColorChanged()));
    ui->redLine->setReadOnly(true);
    ui->greenLine->setReadOnly(true);
    ui->blueLine->setReadOnly(true);
    on_ColorChanged();
    this->serialCom = serialCom;

    // highlights default device
    ui->listWidget->item(0)->setSelected(true);
    ui->listWidget->setCurrentItem(ui->listWidget->item(0));

    // sets default values for default device
    ui->listWidget->item(0)->setData(Qt::UserRole, "A01");

    connect( ui->colorWheelWidget, SIGNAL( colorChange( const QColor & ) ), this, SLOT( updatePalette( const QColor & ) ) );
    connect(this, SIGNAL( houseChange( const QString & ) ), &device, SLOT( setHouse( const QString & ) ) );
    connect(this, SIGNAL( unitChange( const QString & ) ), &device, SLOT( setUnit( const QString & ) ) );
}

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And Device header (class B):

#ifndef DEVICE
#define DEVICE
 
#include "serialcom.h"
 
class Device : public QWidget
{
    Q_OBJECT
 
public:
    explicit Device(QWidget *parent = 0);
    QString getHouse();
    QString getUnit();
 
public slots:
    void setHouse(const QString &);
    void setUnit(const QString &);
 
protected:
 
private:
    QString house;
    QString unit;
 
private slots:
 
};
 
#endif // DEVICE

#ifndef DEVICE
#define DEVICE

#include "serialcom.h"

class Device : public QWidget
{
    Q_OBJECT

public:
    explicit Device(QWidget *parent = 0);
    QString getHouse();
    QString getUnit();

public slots:
    void setHouse(const QString &);
    void setUnit(const QString &);

protected:

private:
    QString house;
    QString unit;

private slots:

};

#endif // DEVICE

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And Device cpp:

#include "device.h"
 
QString Device::getHouse()
{
    return house;
}
 
QString Device::getUnit()
{
    return unit;
}
 
void Device::setHouse(const QString & house_)
{
    house = house_;
    qDebug()<< "\nHouse value is:" << house;
}
 
void Device::setUnit(const QString & unit_)
{
    unit = unit_;
    qDebug()<< "Unit value is:" << unit;
}

#include "device.h"

QString Device::getHouse()
{
    return house;
}

QString Device::getUnit()
{
    return unit;
}

void Device::setHouse(const QString & house_)
{
    house = house_;
    qDebug()<< "\nHouse value is:" << house;
}

void Device::setUnit(const QString & unit_)
{
    unit = unit_;
    qDebug()<< "Unit value is:" << unit;
}

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The full error is:
colorselect.obj:-1: error: LNK2019: unresolved external symbol "public: __cdecl Device::Device(class QWidget *)" (??0Device@@QEAA@PEAVQWidget@@@Z) referenced in function "public: __cdecl ColorSelect::ColorSelect(class QWidget *,class SerialCom *)" (??0ColorSelect@@QEAA@PEAVQWidget@@PEAVSerialCom@@ @Z)

And another related error I get:
debug\colorselect.exe:-1: error: LNK1120: 1 unresolved externals

I can also attach the whole project if you want.

[Vikram.Saralaya]

Where is the Device(QWidget* parent) constructor definition? I can't see it in Device.cpp..

[Leutzig]

Yep, that was it. There wasn't supposed to be a constructor and I completely overlooked the one Qt made in the header. Thanks Vik!