Signal to a custom Slot.

yczo

Hello folks, I'm trying to connect a signal from a thread, to a custom Slot in the MainWindow.
That is my idea:

In the thread:
//*******************************************
char msg[] ="Send info\n";
emit xtring(msg);
//*******************************************
in MainWindow , i have

//*******************************************
connect(mnC,SIGNAL(xtring(QString)),this,SLOT(filterSignal(QString received)),Qt::QueuedConnection);
(in constructor)
//*******************************************

and the function
//*******************************************
void MainWindow::filterSignal(QString received){

string rcv = received.toStdString().c_str();
cerr << rcv << endl;

}
//*******************************************
The console, don't show rcv. I don't undestand why don't works.
Please, can somebody help me?

Thanks in advance

mrjj

@yczo said:

connect(mnC,SIGNAL(xtring(QString)),this,SLOT(filterSignal(QString received)),Qt::QueuedConnection);
(in constructor)

I would expect
SLOT(filterSignal(QString)),
(without the actual parameter name)

also you can do
qDebug() << "con:" << connect(mnC,xxxx)
to see if it returns true for the connection.

yczo

The connection shows false :-(

but why????

I have
//*********************************************
connect(mnC, SIGNAL(xtring(QString)),ui->tBr_2, SLOT(append(QString)),Qt::QueuedConnection);

qDebug() << "con: " << connect(mnC,SIGNAL(xtring(QString)),this,SLOT(filterSignal(QString)),Qt::QueuedConnection);

//**************************************************

the first connection is from the same source to a text browser and works good... Why the second to the custom slot not?

Thank you very much for your help

mrjj

@yczo said:

mnC

u dont show this class.
Does it both have Q_OBJECT macro and a
public signal called
void xtring(QString xx);

?

yczo

that is the class header

class mngCOM : public QThread{
Q_OBJECT
public:
bool exit = false;

void sendMSG(char *msg, short nSend); //ret 0 if err
char *receiveMSG();
mngCOM(QObject *parent);
int searchPort();
~mngCOM();
void run();

signals:
void xtring(QString xtr);
void cnxCom(QString cnxC);
private:
HANDLE handlerP;
DWORD bytesRW, bEvent; //0 initialize muss
char bufferPort[buffS];

HANDLE openPort(char serialPort[],QString &cnxSt);

};

Thank you

beecksche

I had a similiar case, when i want to connect signals/slots between threads. I had to register the metatype. Usually this should be done automatically, but maybe it will help:

Declare the QString outside the class with (http://doc.qt.io/qt-5/qmetatype.html#Q_DECLARE_METATYPE)

Q_DECLARE_METATYPE(QString)

and register it in your constructor (http://doc.qt.io/qt-5/qmetatype.html#qRegisterMetaType-1)

int id = qRegisterMetaType<QString>();

Maybe it will help.

yczo

Thank you very much, I will take a look;

Anymore:
After clean the project un re-compile, I obtained the next warning

C:\Users\ljm\workspace@Qt\project\mainwindow.h:30: warning: Function declaration MainWindow::filterSignal contains extra qualification. Ignoring as signal or slot.

Greetings

mrjj

@yczo said:

Function declaration MainWindow::filterSignal

Sounds like you have

class Mainwindow :
MainWindow::filterSignal() {} << extra qualification
};

in the .h file

yczo

Solved! the error, was.... that i am newbie to Qt.. XD

That in the header from function i had the name from object copied

void MainWindow::filterSignal(QString received);

instead of

void filterSignal(QString received);

but the compiler did not an error show :-(

Greetings and thank you very much.