Need help with signals and slots

Katha99

Hello everyone,

I am a bit lost and confused here and would be very thankful if someone could help me.

I want to call a function after a button is clicked. My program doesn't give me any errors and the Signal and the Slot is connected (I put a bool variable in front of the connect and checked its value. It was true. ), but the function undoOneMove3 won't execute (I don't get the text I put in the function. And I'm pretty sure the output commands are not the problem, because I tried them somewhere else in the program where they worked.)
But I don't find the reason it doesn't work.

Here are parts of the programm:

undomove.hpp

#ifndef UNDOMOVE_H
#define UNDOMOVE_H

#include <stack>
#include <QLabel>
#include "dragwidget.h"

class undoMove3 : public Drag3Widget
{
    Q_OBJECT
public:
    explicit undoMove3(QWidget *parent = nullptr);

private:
    static std::stack<Drag3Widget*> undoStack3;     
    static std::stack< int > undoCoord3x;          
    static std::stack< int > undoCoord3y;

    friend class Drag3Widget;

public slots:
    void undoOneMove3();

};

#endif // UNDOMOVE_H

undomove.cpp

#include "undomove.h"
#include <QTextStream>

undoMove3::undoMove3( QWidget *parent ){ }

// löscht den letzten Spielstein vom Spielfeld und legt ihn auf die Benutzerhand.
void undoMove3::undoOneMove3(){

    if ( undoMove3::undoStack3.empty() )
    {
        QTextStream out(stdout);
        out << QString("undoOneMove3-Function-Beginning");

        QLabel *newIcon = new QLabel( undoMove3::undoStack3.top() );

        int Coord1 = undoMove3::undoCoord3x.top();
        int Coord2 = undoMove3::undoCoord3y.top();
        newIcon->setGeometry( Coord1, Coord2, 75, 75 );

        undoMove3::undoStack3.pop();
        undoMove3::undoCoord3x.pop();
        undoMove3::undoCoord3y.pop();

        newIcon->show();
        newIcon->setAttribute(Qt::WA_DeleteOnClose);

        out << QString("undoOneMove3-Function-End");
    }
    return;
}

std::stack<Drag3Widget*> undoMove3::undoStack3;
std::stack< int > undoMove3::undoCoord3x;
std::stack< int > undoMove3::undoCoord3y;

main.cpp

#include "mainwindow.h"
#include "dragwidget.h"
#include "undomove.h"

#include <QApplication>
#include <QLabel>
#include <QPushButton>
#include <QLayout>
#include <QFrame>
#include <QHBoxLayout>
#include <QDrag>
#include <QMimeData>
#include <QMouseEvent>
#include <QToolButton>
#include <QTextEdit>
#include <QObject>
#include <QTextStream>

#include <QGlobal.h>
#include <QTime>

 int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QWidget* hauptfenster = new QWidget();
    hauptfenster->setGeometry(80,60,1600,900); 

....

    QPushButton* undo = new QPushButton (hauptfenster);
    undo-> setGeometry(1270,670,80,80);
    undo-> setIcon(QPixmap(":/images/retry.png"));
    undo-> setIconSize(QSize(80,80));

    undoMove3 undoMoveObject;
    QObject::connect(undo, &QPushButton::clicked, &undoMoveObject, 
    &undoMove3::undoOneMove3 );

...

hauptfenster->show();

    return a.exec();

sierdzio

@Katha99 said in Need help with signals and slots:

if ( undoMove3::undoStack3.empty() )

Are you sure the stack is empty? If not, your whole code won't be executed.

out << QString("undoOneMove3-Function-Beginning");

There is no need to wrap literals in QString() like this. Standard way of printing is to use qDebug() instead of text stream (but your solution should work).

VRonin

I don't get the text I put in the function.

99.9% chance it's just because undoMove3::undoStack3.empty() returns false. Use a debugger and put a breakpoint before the if is checked.

P.S.
Looks like you are using widgets to do stuff that should be done using the graphics view framework. Might be worth having a stab at redesigning the program from the ground up

Katha99

@sierdzio, @VRonin
Thank you very much.
I dont know why I put that if clause there in the beginning anymore. But actually it doesn't make any sense.... I didn't even look at the if clause while looking for the error...

I tried the code without the if clause and it worked.
Thank you very much for your help.

I will try using qDebug() next time and I will take a look at the Qt Graphics Framework. I don't know it, to be honest.