How to change property of more than one qlineedit at once - c++

Question

I have done some coding for L00 (name of my first QLineEdit).
I want to do the same for other 99 widgets (up to L99). I don't wanna copy paste it 100 hundred times.
void MainWindow::on_L00_returnPressed(){
QString c = ui->L00->text();
char d = QString(c).at(0).toLatin1();
if(d>=65&&d<=90||d>=97&&d<=122)
{
square[0]=d;
ui->MessageBox->setText("Alphabet succesfully entered");
ui->L00->setReadOnly(true);
ui->L00->setStyleSheet("QLineEdit { background: rgb(0, 255, 255);}");
}
else
{
ui->MessageBox->setText("Enter Alphabets Only");
ui->L00->setText("");
}
}

Answer 1

If you add all these widget through Qt Designer the objects will have the same name of the variable, so we can get them through findChild, then apply connect the signal ReturnPressed to a lambda function and not having to create a slot for each QLineEdit.
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
int n = 100;
for(int i=0; i<n; i++){
QString name = QString("L%1").arg(i, 2, 10, QChar('0'));
QLineEdit* w = findChild<QLineEdit *>(name);
connect(w, &QLineEdit::returnPressed, [=](){
QString c = w->text();
char d = QString(c).at(0).toLatin1();
if((d>=65&& d<=90)||(d>=97&&d<=122))
{
square[i]=d;
ui->MessageBox->setText("Alphabet succesfully entered");
w->setReadOnly(true);
w->setStyleSheet("QLineEdit { background: rgb(0, 255, 255);}");
}
else
{
ui->MessageBox->setText("Enter Alphabets Only");
w->clear();
}
});
}
}
Note: I have considered that square[i] corresponds to the QLineEdit L-i.
Another solution is to connect all to the same slot and obtain the object through the function sender().
*.h
private slots:
void onReturnPressed();
*.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
for(QLineEdit* w: findChildren<QLineEdit *>()){
connect(w, &QLineEdit::returnPressed, this, &MainWindow::onReturnPressed);
}
}
void MainWindow::onReturnPressed()
{
QLineEdit* w =qobject_cast<QLineEdit *>(sender());
int i = w->objectName().remove(0, 1).toInt();
QString c = w->text();
char d = QString(c).at(0).toLatin1();
if((d>=65&& d<=90)||(d>=97&&d<=122))
{
square[i]=d;
ui->MessageBox->setText("Alphabet succesfully entered");
w->setReadOnly(true);
w->setStyleSheet("QLineEdit { background: rgb(0, 255, 255);}");
}
else
{
ui->MessageBox->setText("Enter Alphabets Only");
w->clear();
}
}
For old version:
*.h
private slots:
void onReturnPressed();
.cpp
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
int n = 100;
for(int i=0; i<n; i++){
QString name = QString("L%1").arg(i, 2, 10, QChar('0'));
QLineEdit* w = findChild<QLineEdit *>(name);
if(w)
connect(w, SIGNAL(returnPressed()), this, SLOT(onReturnPressed()));
}
}
void MainWindow::onReturnPressed()
{
QLineEdit* w =qobject_cast<QLineEdit *>(sender());
int i = w->objectName().remove(0, 1).toInt();
QString c = w->text();
char d = QString(c).at(0).toLatin1();
if((d>=65&& d<=90)||(d>=97&&d<=122))
{
square[i]=d;
ui->MessageBox->setText("Alphabet succesfully entered");
w->setReadOnly(true);
w->setStyleSheet("QLineEdit { background: rgb(0, 255, 255);}");
}
else
{
ui->MessageBox->setText("Enter Alphabets Only");
w->clear();
}
}

Answer 2

You can use the QObject::findChildren to do so. It must be called from the parent widget (your MainWindow). You can from it connect the QLineEdit individually, or change all values at once.
Example:
for (auto lineEdit : this->findChildren<QLineEdit*>()) {
// connect lineEdit or change values
}

Answer 3

Problem starts with:
I have done some coding for L00 (name of my first QLineEdit) … 99 widgets (up to L99).
This means that you designed your application incorrectly.
I'm almost sure that you should use QTableView or QTableWidget with QAbstractTableModel or QStandartItemModel.
Also setStyleSheet should be applied on QApplication or at least on top level widget. This is how stylesheet is supposed to be used.