Why can't I construct my subclass in QT C++? [duplicate] - c++

Question

This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 7 months ago.
I am working on a project that utilizes a whole suite of custom widget that my company uses.
I am trying to subclass the QLineEdit QWidget so that I can override the default arrow key behavior. It should just behave like a regular QLineEdit.
I then want to use this custom QLineEdit (that I named DataLineEdit), in place of the standard QLineEdits that I dynamically created in another Widget, DataWidget.
I have followed tutorial after tutorial on subclassing, but cannot avoid the error:
undefined reference to "DataLineEdit::DataLineEdit(QWidget*)
My code is below.
datalineedit.h
#ifndef DATALINEEDIT_H
#define DATALINEEDIT_H
#include <QLineEdit>
#include <QWidget>
class DataLineEdit: public QLineEdit
{
Q_OBJECT
public:
explicit DataLineEdit(QWidget *parent = 0);
~DataLineEdit();
protected:
void keyPressEvent(QKeyEvent* event);
signals:
void leftRightOverrideKeyPress(int state);
private:
};
#endif // CUSTOMLINEEDIT_H
datalineedit.cpp
#include "datalineedit.h"
#include<QKeyEvent>
DataLineEdit::DataLineEdit(QWidget*parent) : QLineEdit(parent)
{
}
DataLineEdit::~DataLineEdit()
{
}
void DataLineEdit::keyPressEvent(QKeyEvent *event)
{
if(event->key() == Qt::Key_Left && this->cursorPosition() == 0)
{
emit leftRightOverrideKeyPress(0);
}
else if(event->key() == Qt::Key_Right && this->cursorPosition() == 2)
{
emit leftRightOverrideKeyPress(1);
}
else
{
QLineEdit::keyPressEvent(event);
}
}
datawidget.h
#define DATAWIDGET_H
#include <QFile>
#include <QFileDialog>
#include <QTextStream>
#include <QMessageBox>
#include <QLineEdit>
#include <QObject>
#include <QtCore>
#include <QtGui>
#include <QKeyEvent>
#include <QMainWindow>
#include "datalineedit.h"
extern int focusRow;
extern int focusCol;
extern int numRows;
extern int numBottomRowCols;
extern QLineEdit *focusedLineEdit;
namespace Ui{
class DataWidget;
}
class QLineEdit;
class QLabel;
class DataWidget : public QWidget
{
Q_OBJECT
public:
explicit DataWidget(QWidget *parent = 0);
~DataWidget();
QString data;
protected:
bool eventFilter(QObject *object, QEvent *event);
public slots:
void focusChanged(QWidget *old, QWidget *now);
void arrowKeyNavigation(int state);
void on_applyChangePushButton_clicked();
void setData(QString text);
QString getData();
private slots:
void updateDataGridVisibility();
void on_payloadLineEdit_textChanged(const QString &arg1);
void on_savePushButton_clicked();
void on_openPushButton_clicked();
void on_presetComboBox_currentIndexChanged(int index);
private:
Ui::DataWidget *ui;
QString currentFile = "";
};
#endif // DATAWIDGET_H
datawidget.cpp
#include "datawidget.h"
#include "datawidget.h"
#include "datalineedit.h"
#include <QGridLayout>
#include <QLineEdit>
#include <QGroupBox>
#include <QKeyEvent>
#include <QIntValidator>
int focusRow;
int focusCol;
int numRows;
int numBottomRowCols;
QLineEdit *focusedLineEdit;
enum key_directions
{
arrowLeft = 0,
arrowRight = 1,
arrowUp = 2,
arrowDown = 3
};
enum presets
{
preset1 = 0,
preset2 = 1,
preset3 = 2,
preset4 = 3,
preset5 = 4,
clean = 5,
zeroes = 6
};
DataWidget::DataWidget(QWidget *parent) :
QWidget(parent),
ui(new Ui::DataWidget)
{
ui->setupUi(this);
this->installEventFilter(this);
connect(qApp, SIGNAL(focusChanged(QWidget*, QWidget*)), this, SLOT(focusChanged(QWidget*,QWidget*)));
//payloadLineEdit
ui->payloadLineEdit->setValidator(new QIntValidator(0,64, this));
ui->payloadLineEdit->setFixedSize(20,20);
ui->payloadLineEdit->setTextMargins(0,0,0,0);
//dataGridLayout
ui->dataGridLayout->setAlignment(Qt::AlignLeft);
ui->dataGridLayout->setAlignment(Qt::AlignTop);
for(int i=0; i<4; i++)
{
for(int j=0; j<16; j++)
{
DataLineEdit *lineEdit = new DataLineEdit();
lineEdit->setText("00");//set data default
lineEdit->setInputMask("Hh");//limit to hex values
lineEdit->setFixedSize(20,20);
lineEdit->setTextMargins(0,0,0,0);
lineEdit->setAlignment(Qt::AlignCenter);
lineEdit->setAlignment(Qt::AlignCenter);
connect(lineEdit, SIGNAL(leftRightOverrideKeyPress(int)), this, SLOT(arrowKeyNavigation(int)));
ui->dataGridLayout->addWidget(lineEdit, i, j);
}
}
updateDataGridVisibility();
}
DataWidget::~DataWidget()
{
delete ui;
}
void DataWidget::arrowKeyNavigation(int state)
{
//does something
}

Answer 1

You could edit the class in the following form:
class DataLineEdit: public QLineEdit
{
Q_OBJECT
public:
explicit DataLineEdit(QWidget* parent = 0);
...
and
DataLineEdit::DataLineEdit(QWidget* parent) : QLineEdit(parent)
{
}

Answer 2

Thank you for all the help, it was definitely a linker issue but since I am working within a much larger project, I didn't want to mess with imports or .pro files too much. DataLineEdit is specific to DataWidget, so I simply moved the entire datalineedit.h file into the datawidget.h file at the bottom, and the same for the .cpp files. This avoids any linking all together and keeps things tidier based on the project's file hierarchy.