Some errors in a simple program

tomy

Hi all,
Please consider these .h, .cpp and main,cpp files:

test.h:

#ifndef TEST1_H
#define TEST1_H
#include <QMainWindow>

class QlineEdit;
class QPushButton;

class test1 : public QMainWindow
{
    Q_OBJECT

public:
    test1(QWidget* parent = 0);

private slots:
    void show_clicked();

private:
    int i;
    QlineEdit* line;
    QPushButton* show;
    QPushButton* quit;

};

#endif // TEST1_H

test1.cpp:

#include <QtWidgets>
#include "test1.h"

test1::test1(QWidget* parent)
   : QMainWindow(parent)
{
 i = 5;
 show = new QPushButton(tr("show"));
 quit = new QPushButton(tr("Quit"));
 line = new QlineEdit;

 connect(show, SIGNAL(clicked(bool)), line, SLOT(show_clicked()));
 connect(quit, SIGNAL(clicked(bool)), this, SLOT(close));

 QVBoxLayout* layout = new QVBoxLayout;
 layout->addWidget(line);
 layout->addWidget(show);
 layout->addWidget(quit);
 setLayout(layout);
}

//**********************************

void test1::show_clicked()
{
 line->text(i);
}

and main.cpp:

#include<QApplication>
#include "test1.h"

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    test1* t1 = new test1;
    t1->show();
    return app.exec();
}

I get these errors in the test1.cpp:

test1.cpp:10: error: invalid use of incomplete type 'class QlineEdit'
line = new QlineEdit;

test1.cpp:12: error: no matching function for call to 'test1::connect(QPushButton&, const char*, QlineEdit*&, const char*)'
connect(show, SIGNAL(clicked(bool)), line, SLOT(show_clicked()));*
^
error: no type named 'Object' in 'struct QtPrivate::FunctionPointer<const char>'*

no matching function for call to 'QVBoxLayout::addWidget(QlineEdit&)'
layout->addWidget(line);*

test1.cpp:26: error: invalid use of incomplete type 'class QlineEdit'
line->text(i);

5 errors!

mrjj

@tomy said in Some errors in a simple program:

invalid use of incomplete type 'class QLineEdit'

Means that you need its include file.
It simply only knows its name, not full info.

so you need
#include <QlineEdit>

Also, you have a misstype
line = new QlineEdit;

its with big L

line = new QLineEdit;

so its most likely that.

tomy

@mrjj
Because of forward declarations, it didn't need more includes. I corrected the typos and now it's fine except a way to show an int number in a lineEdit.
I tried to find a function (of lineEdit) for that but couldn't find one!

Thank you for your help.

mrjj

@tomy
To show an int as a string, you can use QString::number

Like
lineEdit->setText( QString::number( int_variable ) );

Note that it wont do right if other locales etc. But I will assume
for your tests, we can ignore that for now.

tomy

Thank you.

I din't understand your comment on not using int values for a lineEdit. Would you please explain it?
If a lineEdit is only good to show texts, what is the standard way to show values on programs, please?

I changed the QPushbutton show to show_number. Then ran the program. It ran successfully but shows only a window!!
Isn't the setLayout() function sufficient to map the widgets on the window when running/showing?

mrjj

@tomy

I din't understand your comment on not using int values for a lineEdit. Would you please explain it?

Its not about the lineEdit. using ::number converts directly to
a text version of the number.
like 7 -> "7".
However, for some other uses, you must take into account how its written. Some countries uses . for thousand like 1.000, other might use , (comma) and so on. 1,000
Qt has other function to convert such numbers besides ::number.
That was what i meant.

tomy

@mrjj

Qt has other function to convert such numbers besides ::number.
That was what i meant.

OK. What function would you use to show a number in a widget, e.g. a lineEdit, please?

And did you read my last question in the prior post please?

mrjj

@tomy
This class
http://doc.qt.io/qt-5/qlocale.html

setLayout(layout); should do it but else try to give widget as parent in ctor
QVBoxLayout* layout = new QVBoxLayout(this); << give parent
and dont do setLayout

tomy

@mrjj

This class
http://doc.qt.io/qt-5/qlocale.html

For showing a number?!

setLayout(layout); should do it but else try to give widget as parent in ctor
QVBoxLayout* layout = new QVBoxLayout(this); << give parent
and dont do setLayout

I declared it like this: QVBoxLayout* layout = new QVBoxLayout(this); and didn't use the setLayout(layout);.
But no changes.
I think the problem is very simple. Please take a look at the codes once gain:

#ifndef TEST1_H
#define TEST1_H
#include <QMainWindow>

class QLineEdit;
class QPushButton;

class test1 : public QMainWindow
{
    Q_OBJECT

public:
    test1(QWidget* parent = 0);

private slots:
    void show_clicked();

private:
    int i;
    QLineEdit* line;
    QPushButton* show_number;
    QPushButton* quit;

};

#endif // TEST1_H

#include <QtWidgets>
#include "test1.h"

test1::test1(QWidget* parent)
    : QMainWindow(parent)
{
  i = 5;
  show_number = new QPushButton(tr("show"));
  quit = new QPushButton(tr("Quit"));
  line = new QLineEdit;

  connect(show_number, SIGNAL(clicked(bool)),
          line, SLOT(show_clicked()));
  connect(quit, SIGNAL(clicked(bool)), this, SLOT(close));

  QVBoxLayout* layout = new QVBoxLayout(this);
  layout->addWidget(line);
  layout->addWidget(show_number);
  layout->addWidget(quit);
  setLayout(layout);
}

//**********************************

void test1::show_clicked()
{
  line->setText(QString::number(i));
}

#include<QApplication>
#include "test1.h"

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);
    test1* t1 = new test1;
    t1->show();
    return app.exec();
}

mrjj

@tomy said in Some errors in a simple program:

For showing a number?!

For correctly formatting numbers as string while considering country norms.

think the problem is very simple. Please take a look at the codes once gain:

Ah its because its a MainWindow
it has special center widget called
http://doc.qt.io/qt-5/qmainwindow.html#centralWidget
which you should set the layout on.
and not the mainwindow itself!!

QVBoxLayout* layout = new QVBoxLayout(this->centralWidget());
layout->addWidget(line);
layout->addWidget(show_number);
layout->addWidget(quit);
~~setLayout(layout);~~ if used MUST be centralWidget()->setLayout(xx)

tomy

@mrjj

QVBoxLayout* layout = new QVBoxLayout(this->centralWidget());
layout->addWidget(line);
layout->addWidget(show_number);
layout->addWidget(quit);
~~setLayout(layout);~~ if used MUST be centralWidget()->setLayout(xx)

Hi,

I used both cases but neither worked for QMainWindow. I had to change it to QDialog. then it worked and showed the widgets.

Incidentally, one of my connects in the code was:

connect(show_number, SIGNAL(clicked(bool)), line, SLOT(show_clicked()));

When I clicked on the show button, nothing was shown in the lineEdit. But when I changed the receiver from line to this, it showed 5. Why please?

mrjj

@tomy said in Some errors in a simple program:

But when I changed the receiver from line to this, it showed 5. Why please?

Well, maybe before the connect was not right.

so if line didnt have show_clicked()

then connect returns false and no connection is made.