How to identify which lineEdit has changed in the ui?

[kishore_hemmady]

I have a ui with 30 lineEdits,When user changes Nth lineEdit value I want to set a bool value_changed_lineEdit_N as true.
I tried
connect(ui->lineEdit,SIGNAL(textChanged(QString),this,value_changed_lineEdit=true);

Is there any way to do this?Please suggest.

[aha_1980]

Hi @kishore_hemmady,

you can try (untested):

connect(u->lineEdit, &QLineEdit::textChanged, this, [this]() {
  value_changed_lineEdit=true;
});

You can make the whole thing more easy by creating the lineEdits in code and use QSignalMapper.

Your whole problem should then be solved with a few lines of code.

Regards

[sierdzio]

Slot has to be a function or a lambda expression. Writing "live code" like this won't work.

One approach would be to store your line edits (pointers to them) in a QVector in the same order that your N numbering has. Then you will be able to check which line edit has fired the signal (use sender() in your slot for that) is the Nth in your vector - and that will give you the "N" number.

Or, instead of declaring 30 boolean members, do this using QHash<QLineEdit*, bool> and store the modification flag in the hash.

[J.Hilk]

To complete the hat-trick,
you can also subclass QLineEdit and make a new signal with an identifier:

class myLineEdit : public QLineEdit
{
    Q_OBJECT
public:
    explicit cLineEdit(QWidget * parent = 0, int Id) :
        QLineEdit(parent), m_Id(id){
        connect(this, SIGNAL(textChanged(QString)), this, SLOT(sendMySignal(QString)) );
   }

private slots:
    void sendMySignal(QString &str){
         emit mySignal(str,m_Id);
    }

signals:
   void mySignal(QString,int);

private:
  int m_Id;
};

[aha_1980]

@J.Hilk: Cool. Haven't though about this.

@kishore_hemmady: If you like to go @J-Hilk's way, you can use the "promote" feature in Qt Designer to change the QLineEdit's to MyLineEdit's

[SGaist]

Hi,

Just one small addition to @J-Hilk suggestion: put the parent parameter as the last one. That's the common way to write constructors with multiple parameters for QObject/QWidget derived classes.