Override a signal

[daviddoria]

I want to set the text of a label when I click a button.

I have a button called 'pushButton' and a label called 'label'.

My form class is like this (buttonform.h):

#ifndef BUTTONFORM_H
 #define BUTTONFORM_H
 
 #include "ui_buttonform.h"
 
 class ButtonForm : public QWidget
 {
     Q_OBJECT
 
 public:
     ButtonForm(QWidget *parent = 0);
 
 private slots:
     //void pushButton_Clicked();
 
 signals:
         void pushButton_Clicked();
 private:
     Ui::ButtonForm ui;
 };
 
 #endif

#ifndef BUTTONFORM_H
 #define BUTTONFORM_H

 #include "ui_buttonform.h"

 class ButtonForm : public QWidget
 {
     Q_OBJECT

 public:
     ButtonForm(QWidget *parent = 0);

 private slots:
     //void pushButton_Clicked();
     
 signals:
         void pushButton_Clicked();
 private:
     Ui::ButtonForm ui;
 };

 #endif

To copy to clipboard, switch view to plain text mode 

In buttonform.cpp, I had this:

#include <QtGui>
 
#include "buttonform.h"
#include <iostream>
 
ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);
}
 
void ButtonForm::pushButton_Clicked()
 {
   ui.label->setText("hello");
 }

#include <QtGui>

#include "buttonform.h"
#include <iostream>

ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);
}

void ButtonForm::pushButton_Clicked()
 {
   ui.label->setText("hello");
 }

To copy to clipboard, switch view to plain text mode 

but it tells me that pushButton_Clicked() is already defined in moc_buttonform.cxx.

How should I go about doing this?

Thanks!

Dave

[Ginsengelf]

Hi, you are implementing a signal, which is already done by the moc for you and therefore you get the error.
I think what you want is the line you commented: a slot to connect the button's clicked() signal.

Ginsengelf

[daviddoria]

Ok, I guess the reason I didn't know how to do that is that I didn't know how to associate the slot with a particular widget (the pushButton). I think the answer is that you don't - you just associate it with the form:

The problem now is that it says "No such slot ButtonForm:ushButton_SetLabelText(QString& txt)

Here is what I have:

buttonform.cpp

#include <QtGui>
 
#include "buttonform.h"
#include <iostream>
 
ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);
 
 
   connect( this->ui.pushButton, SIGNAL( clicked() ), this, SLOT(pushButton_SetLabelText(QString& txt)) );
 
}
 
void ButtonForm::pushButton_SetLabelText(QString& txt)
 {
   this->ui.label->setText(txt);
 }

#include <QtGui>

#include "buttonform.h"
#include <iostream>

ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
    ui.setupUi(this);
    
    
   connect( this->ui.pushButton, SIGNAL( clicked() ), this, SLOT(pushButton_SetLabelText(QString& txt)) );
     
}

void ButtonForm::pushButton_SetLabelText(QString& txt)
 {
   this->ui.label->setText(txt);
 }

To copy to clipboard, switch view to plain text mode 

buttonform.h

#ifndef BUTTONFORM_H
 #define BUTTONFORM_H
 
 #include "ui_buttonform.h"
 
 class ButtonForm : public QWidget
 {
     Q_OBJECT
 
 public:
     ButtonForm(QWidget *parent = 0);
 
 private slots:
     void pushButton_SetLabelText(QString& txt);
 
 signals:
        //void pushButton_Clicked();
 private:
     Ui::ButtonForm ui;
 };
 
 #endif

#ifndef BUTTONFORM_H
 #define BUTTONFORM_H

 #include "ui_buttonform.h"

 class ButtonForm : public QWidget
 {
     Q_OBJECT

 public:
     ButtonForm(QWidget *parent = 0);

 private slots:
     void pushButton_SetLabelText(QString& txt);
     
 signals:
        //void pushButton_Clicked();
 private:
     Ui::ButtonForm ui;
 };

 #endif

To copy to clipboard, switch view to plain text mode 

main.cpp

#include <QApplication>
 
 #include "buttonform.h"
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     ButtonForm buttonform;
 
     buttonform.show();
     return app.exec();
 }

#include <QApplication>

 #include "buttonform.h"

 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
     ButtonForm buttonform;
     
     buttonform.show();
     return app.exec();
 }

To copy to clipboard, switch view to plain text mode 

I feel like this is very close!

Thanks for your help,

Dave

[daviddoria]

Ah, got it. The problem was the Clicked() signal did not pass a QString

I changed it to:

void pushButton_SetLabelText();

void pushButton_SetLabelText();

To copy to clipboard, switch view to plain text mode 

and

ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
  ui.setupUi(this);
  connect( this->ui.pushButton, SIGNAL( clicked() ), this, SLOT(pushButton_SetLabelText()) );
 
 
 
}
 
void ButtonForm::pushButton_SetLabelText()
 {
   this->ui.label->setText("hello");
 }

ButtonForm::ButtonForm(QWidget *parent)
    : QWidget(parent)
{
  ui.setupUi(this);
  connect( this->ui.pushButton, SIGNAL( clicked() ), this, SLOT(pushButton_SetLabelText()) );
  
  
     
}

void ButtonForm::pushButton_SetLabelText()
 {
   this->ui.label->setText("hello");
 }

To copy to clipboard, switch view to plain text mode 

I thought one of the main points of the Signal/Slot idea was to stop type problems like this (e.g. passing nothing to something expecting a QString)?

Dave

[squidge]

You don't need the connect call, just name your function like so:

void on_pushButton_clicked()
{
// foo
}

void on_pushButton_clicked()
{
// foo
}

To copy to clipboard, switch view to plain text mode 

and everything is done for you

You only need the connect call if you want to call your function something different than the normal.