QT slots and signals fail

Question

Hi there i got problem with signal and slots in qt. In main i have created object of mainwindow. in mainwindow.cpp i creating object of another class(modbus_tcp). i also creating connection here

void MainWindow::on_ConnectB_clicked()
{

    modbus_tcp appts;
    appts.slave();
    connect(&appts,SIGNAL(msgSended(QString)),this,SLOT(msgEdit(QString)));
}

between slot declared in mainwindow.cpp/h

public slots:
void msgEdit(QString m);

void MainWindow::msgEdit(QString m)
{
ui->sendEdit->setText(m);
ui->recvEdit->setText(m);
//QMessageBox::information(0,"bad", "nope nope nope");
}

and signal declared in modbus_tcp.h

signals:
void msgSended(QString);

next i emiting signal in modbus_tcp.cpp

emit msgSended("asdasd");

and nothing happen

when i trying to emit in mainwindow.cpp its working

any ideas ?

Answer 1

void MainWindow::on_ConnectB_clicked()
{

    modbus_tcp appts;
    appts.slave();
    connect(&appts,SIGNAL(msgSended(QString)),this,SLOT(msgEdit(QString)));
}

appts was created in stack, so it will be deleted at the end of slot execution. Try to create it in the heap(try to use pointer).

void MainWindow::on_ConnectB_clicked()
{

    modbus_tcp *appts = new modbus_tcp;
    connect(appts,SIGNAL(msgSended(QString)),this,SLOT(msgEdit(QString)));//first!
    appts->slave();//now you can call it
}

Use pointers, but first of all connect , and after this call slave . You emit signal in slave , but there is no connection in this time. You should do connection firstly and after that, you will be able to catch signals.