Is this no longer exist?

[hutigers]

I am using Qt 4.6.2 and I am reading the book "C++ GUI Programming with Qt 4" the first Edition.
In the book, they said that
In the constructor, we call setupUi() to initialize the form. Thanks to multiple inheritance, we can access Ui::GoToCellDialog's members directly. After creating the user interface, setupUi() will also automatically connect any slots that follow the naming convention on_objectName_signalName() to the corresponding objectName's signalName() signal. In our example, this means that setupUi() will establish the following signalslot connection:

connect(lineEdit, SIGNAL(textChanged(const QString &)),
this, SLOT(on_lineEdit_textChanged()));



However, it didn't work unless I wrote the connect manually. Is that changed?

my header file

#ifndef GOTOCELLDIALOG_H
#define GOTOCELLDIALOG_H
#include <QDialog>
#include "ui_gotocelldialog.h"
class GoToCellDialog : public QDialog, public Ui::GoToCellDialog
{
    Q_OBJECT
public:
            GoToCellDialog(QWidget *parent = 0);
private slots:
    void on_lineEdit_textChange();
};
#endif // GOTOCELLDIALOG_H 

my cpp file

#include <QtGui>
#include "gotocelldialog.h"
GoToCellDialog::GoToCellDialog(QWidget *parent)
    : QDialog(parent)
{
    setupUi(this);
    QRegExp regExp("[A-Za-z][1-9][0-9]{0,2}");
    lineEdit->setValidator(new QRegExpValidator(regExp, this));
    connect(okButton, SIGNAL(clicked()), this, SLOT(accept()));
    connect(cancelButton, SIGNAL(clicked()), this, SLOT(reject()));
//unless I wrote the following connect manually, the okButton would be never enabled.
    connect(lineEdit, SIGNAL(textChanged(QString)), this, SLOT(on_lineEdit_textChange()));
}
void GoToCellDialog::on_lineEdit_textChange()
{
    okButton->setEnabled(lineEdit->hasAcceptableInput());
} 

and the main file:

#include <QApplication>
//#include <QDialog>
//#include <ui_gotocelldialog.h>
#include "gotocelldialog.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    //Ui::GoToCellDialog ui;
    //QDialog *dialog = new QDialog;
    //ui.setupUi(dialog);
    //dialog->show();
    GoToCellDialog *dialog = new GoToCellDialog;
    dialog->show();
    return app.exec();
} 

Anyone help is appreciated.

[divanov]

You have a typo in slot's name.

[hutigers]

problem solved. It should be void on_lineEdit_textChanged(). I forgot the d. And since textChange was not a signal of lineEdit, the on_lineEdit_textchange became a normal slot. =.=

Thanks for all replies.

[danhicksbyron]

I find it's worthwhile to capture the return code from connect and test it with a Q_ASSERT, to catch misspellings and name changes that break connections.

(Note: Don't do "Q_ASSERT(connect(...));", since the connect will not be executed in final code where asserts are disabled. Rather do "bool ok = connect(...); Q_ASSERT(ok);".)

[axeljaeger]

I find it's worthwhile to capture the return code from connect and test it with a Q_ASSERT, to catch misspellings and name changes that break connections.)

Do you have a pattern for this? I like your idea but I usually have around 10 connect statements in a single function and I dont want to have 10 bools just for checking the connects. Do you reuse your ok variable in this case or is there another solution?

[divanov]

The test code:

#include <QApplication>
#include <QDebug>

#include "widget.h"

int
main (int argc, char **argv)
{
    QApplication app(argc, argv);
    Widget w;

    w.show();

    return app.exec();
}

#ifndef WIDGET_H
#define WIDGET_H

#include <QLineEdit>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent=0);

public slots:
    void on_lineEdit_textChange();

private:
    QLineEdit *lineEdit;
};

#endif //WIDGET_H

#include <QDebug>

#include "widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    lineEdit = new QLineEdit(this);
    QMetaObject::connectSlotsByName(this);
}

void Widget::on_lineEdit_textChange()
{
    qDebug() << __PRETTY_FUNCTION__;
}

What happens when I run the test application:

$ ./signals 
QMetaObject::connectSlotsByName: No matching signal for on_lineEdit_textChange()

[danhicksbyron]

Do you have a pattern for this? I like your idea but I usually have around 10 connect statements in a single function and I dont want to have 10 bools just for checking the connects. Do you reuse your ok variable in this case or is there another solution?

Well, you can do:

bool ok;
ok = connect(...);
Q_ASSERT(ok);
ok = connect(...);
Q_ASSERT(ok);
...

Probably a dozen other options. Among which is to create an assertConnect method:

void MyClass::assertConnect(bool ok) {
Q_ASSERT(ok);
}

then code:

assertConnect(connect(...));
...

[divanov]

Well, you can do...

Do you dislike simple ways?

[danhicksbyron]

The guy asked for options and I gave him some. What's your problem with that???

[divanov]

The guy asked for options and I gave him some. What's your problem with that???

Other people may learn from your words.