[solved] Inheritance of QSerialPort question

[deleted28]

Hello,
i want to make a customclass inheriting QSerialPort and have problems.
i get error messages when build:
@.../BallTest_q001/main.cpp:19: error: invalid use of 'this' in non-member function
TheBall ball = new TheBall(this);
^@

and with line 9
@ TheBall ball = new TheBall();@
@...l/BallTest_q001/main.cpp:18: error: no matching function for call to 'TheBall::TheBall()'
TheBall ball = new TheBall();
^@

What is the problem and how to solve ?
main.cpp
@#include <QCoreApplication>
#include <QObject>
#include <theball.h>

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

TheBall ball = new TheBall(this);

return a.exec();

}
@

theball.h
@#include <QObject>
#include <QtSerialPort/QSerialPort>
#include <QtSerialPort/QSerialPortInfo>

class TheBall : public QSerialPort
{
Q_OBJECT

public:
explicit TheBall(QObject *parent);

~TheBall();

};@

theball.cpp
@#include "theball.h"

TheBall::TheBall(QObject *parent)
: QSerialPort(parent)
{

}

TheBall::~TheBall()
{

}@
project.pro
@QT += core
QT += serialport
QT -= gui

TARGET = BallTest_q001

CONFIG += console
CONFIG -= app_bundle

TEMPLATE = app

SOURCES += main.cpp
theball.cpp

HEADERS +=
theball.h@

rhx wally

[SGaist]

Hi,

There's no "this" in main.

main is purely a function and "this" represent the current object you're into. Also note that you should pass a QObject as parameter and again main is not one.

@
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
TheBall ball;
return a.exec();
}@

would be enough. If you really want to allocate ball on the heap then you must also delete it before returning the result of a.exec()

[deleted28]

@#include <QCoreApplication>
#include <QObject>
#include <theball.h>

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

TheBall ball;

return a.exec();

}
@

@.../BallTest_q001/main.cpp:18: error: no matching function for call to 'TheBall::TheBall()'
TheBall ball;
^@

what, when i do a GUI application and construct ball in MainWindow.cpp
MainWindow is an Object and i can use "this", right ?

[SGaist]

Because TheBall's constructor requires a QObject * to be passed, either give it a default value of 0 or give ball the address of a QObject.

MainWindow is a class, main(int argc, char*argv[]) is a function

[deleted28]

found reason for problems when using Gui and MainWindow class:
in BallTest.pro

this gives errors:
@QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets serialport@

rhis is OK :
@QT += core gui
QT += serialport

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets@

needless to say, i do not know why :)

[SGaist]

You're using Qt 4 and that check verifies if your are using Qt 5. If it's the case the new widgets module is added (meaningful only if you are doing a widget based application). With Qt 4 the widgets are in the gui module.

[deleted28]

@SGaist

i got both (console and Gui) work now. thanks for help!
Does it make sense to post the working results here or
this not wanted ?
If yes, is there a way to post entire project folder ?

[SGaist]

Sure you can, generally you would post the relevant piece of code