Qt Signal Slot Undefined Reference
Hi,
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thank you already for investing time to help me finding a solution to my problem. I did research on the web and did not find any idea how to handle my errors. I do voluntary work for a youth organization and I try to help them out with making a program for easier handling with all the finance things. Since we do not have any programmer in our organization I try to deeper my knowledge and ofcourse help the group. I do have basic knowledge in C/C++.
I try to make a GUI with which it is possible and easy!( by clicking buttons and filling in gaps) to save a new payment and later (at the end of the year) make a financial report. I wanted to use structs with IDs for every payment. The IDs should link every payment to a project and pay office. I know it is a lot of text for you to read and any kind of idea how to better my concept and my existing problems would help me to better the final product. All in all it should in the end make a nice Excel table for our chairmain.
Connecting in Qt 5. There are several ways to connect a signal in Qt 5. Qt 5 continues to support the old string-based syntax for connecting signals and slots defined in a QObject or any class that inherits from QObject (including QWidget). Qt: Connecting signals and slots. Tag: c,qt,signals,slot. I have a MainWindow that contains a custom widget with a QTextEdit in it. I would like to create a signal/slot between the MainWindow and the QTextEdit. In MainWindow I have: QObject::connect(ui-Header, SIGNAL(ui-Header-getTextWidget-textChanged), this, // this: MainWindow.
I did start with this code, trying to make just one button (signal slot) work and the errors appeared when building.
The errors are in the pushbutton.cpp, line 3 and 18.
C:QtTools...pushbutton.cpp:3: Fehler:undefined reference to `vtable for pushbutton'
C:QtTools...pushbutton.cpp:18: Fehler:undefined reference to `vtable for pushbutton'
collect2.exe:-1: Fehler:error: ld returned 1 exit status
headers:
-mainwindow.h
-pushbutton.h
sourcecode:
-main.cpp
-mainwindow.cpp
-pushbutton.cpp
@#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
@
@#ifndef PUSHBUTTON_H
#define PUSHBUTTON_H
#include <QObject>
#include <QString>
class pushbutton : public QObject
{
Q_OBJECT
public:
pushbutton(QObject *parent = 0);
~pushbutton();
//public slots:
//void setValue(int value);
//signals:
//void valueChanged(int newValue);
//private:
};
#endif // pushbutton_H
@
@#include 'mainwindow.h'
#include 'pushbutton.h'
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
//pushbutton cPus;
//------------------------------
struct structId{
int iIDa;
int iIDb;
int iIDc;
char sIDa[50];
char sIDb[50];
char sIDc[50];
int ivalue;
}StructFirst;
}
@
@#include 'mainwindow.h'
#include 'ui_mainwindow.h'
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
@
@#include 'pushbutton.h'
*pushbutton::pushbutton(QObject parent):QObject(parent)
{
//createID();
//Variablen
}
void pushbutton::createID()
{
int iIda = 0;
int iIdb = 0;
int iIdc = 0;
}
pushbutton::~pushbutton()
{
}
@
I have a MainWindow that contains a custom widget with a QTextEdit in it. I would like to create a signal/slot between the MainWindow and the QTextEdit.
In MainWindow I have:
But this does not work. Is it even possible to create such signal/slot combination?
why bother - let Qt do all the magic :) Just name your slot (in the mainWindow) like that:
And you're done. More info here: http://doc.qt.io/qt-5/qmetaobject.html#connectSlotsByName important: 'object name' part means name of the object - not variable name. If you design your window in QtDesigner it should be set (in ui.setupUi method). if not - set it manually (by calling setObjectName
Just watch out for number of arguments in your slot. Here's what I do: I simply copy the signal prototype (from from header or the doc - eg: http://doc.qt.io/qt-5/qabstractitemmodel.html#dataChanged - watch out again for the weird whitespace between '::' and method name [some kind of an unbreakable-zerowidth-space] - only present when copying from v5.x doc), and prepend it with on_objectName_. That guarantees, that your slot will be ok to connect it to the signal
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