Signals won't trigger see code below (I am using Qt on OS X 10.8 amples app are working fine but this one won't...)

lvignals

@#ifndef MAINWINDOW_H
#define MAINWINDOW_H

//#include <QDialog>
#include <QtGui>

class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;

class MainWindow : public QDialog
{
Q_OBJECT

public:
MainWindow(QWidget *parent = 0);
~MainWindow();

signals:
void findNext(const QString &str, Qt::CaseSensitivity cs);
void findPrevious(const QString &str, Qt::CaseSensitivity cs);
void textChanged(const QString &str);

private slots:
void findClicked();
void enableFindButton(const QString &text);

private:
QLabel *debugLabel;
QLabel *label;
QLineEdit *lineEdit;
QCheckBox *caseCheckBox;
QCheckBox *backwardCheckBox;
QPushButton *findButton;
QPushButton *closeButton;
};

#endif // MAINWINDOW_H

#include <QtGui>
#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent) : QDialog(parent)
{
debugLabel = new QLabel(tr("no debug info yet..."));
label = new QLabel(tr("Find &what"));
lineEdit = new QLineEdit;
label->setBuddy(lineEdit);

caseCheckBox = new QCheckBox(tr("Match &case"));
backwardCheckBox = new QCheckBox(tr("Search &backward"));

findButton = new QPushButton(tr("&Find"));
findButton->setDefault(true);
findButton->setEnabled(false);

closeButton = new QPushButton(tr("Close"));


/*bool r=false;
r = QObject::connect(pObj1,SIGNAL(signalStuff()),pObj2,SLOT(gotStuff()));
Q_ASSERT(r);*/

bool r=false;
r = connect(lineEdit, SIGNAL(textChanged(QString &text)), this, SLOT(enableFindButton(QString &text)));
Q_ASSERT(r);
connect(findButton, SIGNAL(clicked()), this, SLOT(findClicked()));
connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));

QHBoxLayout *topLeftLayout = new QHBoxLayout;
topLeftLayout->addWidget(label);
topLeftLayout->addWidget(lineEdit);
QVBoxLayout *leftLayout = new QVBoxLayout;
leftLayout->addLayout(topLeftLayout);
leftLayout->addWidget(caseCheckBox);
leftLayout->addWidget(backwardCheckBox);
leftLayout->addWidget(debugLabel);
QVBoxLayout *rightLayout = new QVBoxLayout;
rightLayout->addWidget(findButton);
rightLayout->addWidget(closeButton);
rightLayout->addStretch();
QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->addLayout(leftLayout);
mainLayout->addLayout(rightLayout);
setLayout(mainLayout);

setWindowTitle(tr("Find"));
setFixedHeight(sizeHint().height());

}

MainWindow::~MainWindow()
{

}

void MainWindow::findClicked()
{
debugLabel->setText(tr("findClicked()"));
QString text = lineEdit->text();
Qt::CaseSensitivity cs = caseCheckBox->isChecked()?Qt::CaseSensitive:Qt::CaseInsensitive;
if (backwardCheckBox->isChecked()) {
emit findPrevious(text, cs);
} else {
emit findNext(text, cs);
}
}

void MainWindow::enableFindButton(const QString &text) {
debugLabel->setText(tr("enableFindButton()"));
findButton->setEnabled(!text.isEmpty());
}

@

Thanks for your help,
Ludovic Vignals

lvignals

Ok found my two problems:

only custom signals need to be declared in class header file so I removed th below signal declaration
@
//void textChanged(const QString &str);
@
in the connect() that takes signal and slot with parameters I did not include the const keywork in front of the arguments the changed line look like this:
@
connect(lineEdit, SIGNAL(textChanged(const QString&)), this, SLOT(enableFindButton(const QString&)));
@

After making those changes the connection worked as expected.
Ludovic Vignals

koahnig

You need to match the call pattern exactly as it is.
The documentation of the "textChanged signal":http://qt-project.org/doc/qt-4.8/qlineedit.html#textChanged sais (const QString &), but you used (QString &). You should also leave the variable's name away.

rewrite to
@
bool r=false;
r = connect(lineEdit, SIGNAL(textChanged(const QString &)), this, SLOT(enableFindButton(const QString &)));
Q_ASSERT(r);
@
The "signal clicked":http://qt-project.org/doc/qt-4.8/qabstractbutton.html#clicked has a bool in the call list. Use "pressed" or "released" signal. Their parameter list is empty.

[too late]