connect signal (Qstring) whit slot (String) of 2 different class - c++

Question

i have 2 class : Class MaFentre and Code
code.h :
class Code : public QObject {
public :
explicit Code(Q3DScatter *scatter);
public slots:
std::vector<point> readingData(std::string inputFileName);
}
MaFenetre.h :
class MaFenetre : public QWidget
{ Q_OBJECT
public:
MaFenetre();
private:
QLineEdit *entry1;
}
Code.cpp :
std::vector<point> Code::readingData(std::string inputFileName){
// i read a file here
}
i created the Code class object in the constructor of the class MaFenetre
Code *modifier = new Code(graph);
for making connection between slot and signal
QObject::connect(entry1, SIGNAL(textChanged(QString)),modifier, SLOT(readingDara(std::string inputFileName)))
i know the parameters must be of the same type , for that i try to code :
QObject::connect(entry, SIGNAL(textChanged(QString.toStdString)),modifier, SLOT(readingDara(std::string inputFileName)))
but it doesnt work

Answer 1

Your signal and slot arguments are not compatible.
You can do this workaround with the lambda function
Code *modifier = new Code();
MaFenetre * poMaFenetre = new MaFenetre();
connect(poMaFenetre->Entry(), &QLineEdit::textChanged,
[modifier](const QString & oText)
{
std::vector<int> data = modifier->readingData(oText.toStdString());
// Handle data here...
});
In the MaFenetre
class MaFenetre : public QWidget
{
Q_OBJECT
public:
MaFenetre() {entry1.reset(new QLineEdit());}
QLineEdit *Entry() {return entry1.data();}
private:
QScopedPointer<QLineEdit> entry1;
};

Answer 2

Using signals and slots it's not the same as calling function and pass parameters.
At first signal and slot must have same parameters type, means they must be defined with same parameters. In your case you have to change your slot to fit possible signals. Also note that returned value is useless in case of slot invoking, so better way is to keep you reading function as is, move it to private area, and create wrapper slot:
void Code::readingDataSlot(QString inputFileName)
{
std::vector<point> result = readingData( inputFileName.toStdString() );
// Do what ever you need with result vector
}
and connect it to signal.
connect(entry1, SIGNAL(textChanged(QString)),modifier, SLOT(readingDataSlot(QString)));