Using enum as parameter to slot functions

[Ponnytail]

I've run into some trouble with signals and slots. I've successfully used them in my application so far but when I wanted to call a slot function with an enum things seemed to get a lot harder. After reading around the net trying to understand what difference an enum parameter make I came up with the following code I thought was gonna work.

I created a new header file just for my enum:
Arrows.h

#ifndef ARROWS_H
#define ARROWS_H
 
#include <QtCore>
 
enum Arrow
{
    NO_ARROW,
    DIAG_DOWN_RIGHT,
    DIAG_DOWN_LEFT,
    DIAG_UP_RIGHT
};
 
Q_DECLARE_METATYPE(Arrow)
 
#endif // ARROWS_H

#ifndef ARROWS_H
#define ARROWS_H

#include <QtCore>

enum Arrow
{
    NO_ARROW,
    DIAG_DOWN_RIGHT,
    DIAG_DOWN_LEFT,
    DIAG_UP_RIGHT
};

Q_DECLARE_METATYPE(Arrow)

#endif // ARROWS_H

To copy to clipboard, switch view to plain text mode 

The header file which declares the slot function looks like this:
CrosswordArea.h

#ifndef CROSSWORDAREA_H
#define CROSSWORDAREA_H
 
#include "Arrows.h"
(...)
 
class CrosswordArea : public QWidget
{
    Q_OBJECT
    Q_ENUMS(Arrow)
 
(...)
 
public slots:
    (...)
    void setArrow(Arrow a);
 
(...)
};
 
#endif // CROSSWORDAREA_H

#ifndef CROSSWORDAREA_H
#define CROSSWORDAREA_H

#include "Arrows.h"
(...)

class CrosswordArea : public QWidget
{
    Q_OBJECT
    Q_ENUMS(Arrow)

(...)

public slots:
    (...)
    void setArrow(Arrow a);

(...)
};

#endif // CROSSWORDAREA_H

To copy to clipboard, switch view to plain text mode 

Slot implementation (I'm not sure if I need qRegisterMetaType here)
CrosswordArea.cpp

#include "Arrows.h"
#include "CrosswordArea.h"
(...)
 
CrosswordArea::CrosswordArea(QString str)
{
    qRegisterMetaType<Arrow>("Arrow");
    (...)
}
 
(...)
 
void CrosswordArea::setArrow(Arrow a)
{
    marked->setArrow(a);
}

#include "Arrows.h"
#include "CrosswordArea.h"
(...)

CrosswordArea::CrosswordArea(QString str)
{
    qRegisterMetaType<Arrow>("Arrow");
    (...)
}

(...)

void CrosswordArea::setArrow(Arrow a)
{
    marked->setArrow(a);
}

To copy to clipboard, switch view to plain text mode 

The slot is connected to a couple of buttons.
ButtonArea.cpp

#include "Arrows.h"
#include "CrosswordArea.h"
(...)
 
ButtonArea::ButtonArea(CrosswordArea *cwArea)
{
    qRegisterMetaType<Arrow>("Arrow");
    (...)
 
    connect(letter2clue, SIGNAL(clicked()), cwArea, SLOT(setClue())); //works
    connect(clue2letter, SIGNAL(clicked()), cwArea, SLOT(setLetter())); //works
    connect(merge, SIGNAL(clicked()), cwArea, SLOT(merge())); //works
    connect(yellowMark, SIGNAL(clicked()), cwArea, SLOT(yellowMark())); //works
    connect(diagDRArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work
    connect(diagDLArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work
    connect(diagURArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work
 
    (...)
}

#include "Arrows.h"
#include "CrosswordArea.h"
(...)

ButtonArea::ButtonArea(CrosswordArea *cwArea)
{
    qRegisterMetaType<Arrow>("Arrow");
    (...)

    connect(letter2clue, SIGNAL(clicked()), cwArea, SLOT(setClue())); //works
    connect(clue2letter, SIGNAL(clicked()), cwArea, SLOT(setLetter())); //works
    connect(merge, SIGNAL(clicked()), cwArea, SLOT(merge())); //works
    connect(yellowMark, SIGNAL(clicked()), cwArea, SLOT(yellowMark())); //works
    connect(diagDRArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work
    connect(diagDLArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work
    connect(diagURArrow, SIGNAL(clicked()), cwArea, SLOT(setArrow(Arrow))); //doesn't work

    (...)
}

To copy to clipboard, switch view to plain text mode 

Running this doesn't cause an error but rather a warning.

QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)
QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)
QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)

QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)
QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)
QObject::connect: Incompatible sender/receiver arguments
        QPushButton::clicked() --> CrosswordArea::setArrow(Arrow)

To copy to clipboard, switch view to plain text mode 

I'm doing something terribly wrong. Before I start to guess solutions, messing up my code in hope to get lucky I thought I'd ask you guys first.
What have I done wrong and how can I make my slot function call correct?

Thanks!

[Lesiok]

You are trying to connect signal without parameter to slot with parameter. This is impossible. Parameters of signal and slot must be the same type. I think that QSignalMapper is what you need.

[Ponnytail]

Thanks Lesiok, a QSignalMapper worked great. I didn't know the parameters of the signal had to be the same as the parameters for the slot. Thanks for the clarification!

My button connection now looks like this.
ButtonArea.cpp

#include "Arrows.h"
#include "CrosswordArea.h"
 
(...)
 
ButtonArea::ButtonArea(CrosswordArea *cwArea)
{
    qRegisterMetaType<Arrow>("Arrow");
    sigMapper = new QSignalMapper(this);
 
    (...)
 
    connect(diagDRArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));
    connect(diagDLArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));
    connect(diagURArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));
 
    sigMapper->setMapping(diagDRArrow, "DIAG_DOWN_RIGHT");
    sigMapper->setMapping(diagDLArrow, "DIAG_DOWN_LEFT");
    sigMapper->setMapping(diagURArrow, "DIAG_UP_RIGHT");
 
    connect(sigMapper, SIGNAL(mapped(QString)), cwArea, SLOT(setArrow(const QString &)));
 
    (...)
}

#include "Arrows.h"
#include "CrosswordArea.h"

(...)

ButtonArea::ButtonArea(CrosswordArea *cwArea)
{
    qRegisterMetaType<Arrow>("Arrow");
    sigMapper = new QSignalMapper(this);
    
    (...)

    connect(diagDRArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));
    connect(diagDLArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));
    connect(diagURArrow, SIGNAL(clicked()), sigMapper, SLOT(map()));

    sigMapper->setMapping(diagDRArrow, "DIAG_DOWN_RIGHT");
    sigMapper->setMapping(diagDLArrow, "DIAG_DOWN_LEFT");
    sigMapper->setMapping(diagURArrow, "DIAG_UP_RIGHT");

    connect(sigMapper, SIGNAL(mapped(QString)), cwArea, SLOT(setArrow(const QString &)));

    (...)
}

To copy to clipboard, switch view to plain text mode 

It feels a bit weird to use enums now though because in my CrosswordArea.cpp I have to map strings to their corresponding enum.
CrosswordArea.cpp

(...)
 
CrosswordArea::CrosswordArea(QString str)
{
    qRegisterMetaType<Arrow>("Arrow");
    arrowMap = new QMap<QString, Arrow>;
    arrowMap->insert("DIAG_DOWN_RIGHT", DIAG_DOWN_RIGHT);
    arrowMap->insert("DIAG_DOWN_LEFT", DIAG_DOWN_LEFT);
    arrowMap->insert("DIAG_UP_RIGHT", DIAG_UP_RIGHT);
 
    (...)
}
 
void CrosswordArea::setArrow(const QString &str)
{
    marked->setArrow(arrowMap->take(str));
}

(...)

CrosswordArea::CrosswordArea(QString str)
{
    qRegisterMetaType<Arrow>("Arrow");
    arrowMap = new QMap<QString, Arrow>;
    arrowMap->insert("DIAG_DOWN_RIGHT", DIAG_DOWN_RIGHT);
    arrowMap->insert("DIAG_DOWN_LEFT", DIAG_DOWN_LEFT);
    arrowMap->insert("DIAG_UP_RIGHT", DIAG_UP_RIGHT);

    (...)
}

void CrosswordArea::setArrow(const QString &str)
{
    marked->setArrow(arrowMap->take(str));
}

To copy to clipboard, switch view to plain text mode 

This works perfectly fine.

Problem SOLVED!

[anda_skoa]

You could also use setMapping(QObject*, int) using the enum values for the int argument and connect to the mapped(int) signal

Cheers,
_

[Ponnytail]

Oh of course! That saves a lot of code. Thanks anda_skoa!