I have an Error in my terminal :device not open- but usually it works...C++

[RuWex]

Hi:)
I have an intersting problem
Im doing a terminal application,
and the terminal work well.
my problem is when Im reading from file and send the letters to the terminal,
then there is that error(in the debug, the program doesnt failed):
QIODevice::write (QSerialPort): device not open
my code:
mainWindow.cpp:

void MainWindow::writeData(const QByteArray &data)
{
    m_serial->write(data);
}

sendCommand.cpp:

void SendCommands::StartToSendCommand( QString fileName)/
{
        QFile file(fileName);
        if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
            return;


        QTextStream in(&file);
        QString line;
        while (!in.atEnd()) {

            line = in.readLine();

            for(int i=0; i< line.length(); ++i)
            {

                QString letter= (QString)line[i];
                MainWindow *mainWind= new MainWindow();
                mainWind->WriteData(letter.toLatin1());

            }
            QApplication::processEvents();


        }


}

but as I said the function usually works except when I run it on the StartToSendCommand function

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

Do you have any Idea how to get the instance that already open?

Like I said, do not try to pass or access the MainWindow instance you have created to MainSendCommand (or any other class). A good rule of thumb is do not allow yourself to go #include "mainwindow.h" in any file other than mainwindow.cpp, then you can never access it from elsewhere.

Assuming you create the MainSendCommand instance from your MainWindow (right?). So pass the serial port instance instead. Like maybe:

// Somewhere in `MainWindow`
mainSendCommand = new MainSendCommand(m_serial);

MainSendCommand::MainSendCommand(QSerialPort *serial)
{
    sendCommand= new SendCommands(serial);
}

SendCommands::SendCommands(QSerialPort *serial)
{
    this->m_serial = serial;
}

void SendCommands::StartToSendCommand( QString fileName)
{
    m_serial->write();
}

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

MainWindow *mainWind= new MainWindow();

What do you think is going to happen if you create a brand new MainWindow each time round the loop for each character?? It's totally the wrong concept, and MainWindow::m_serial will not be open.

Your SendCommands class should not even be attempting to access any MainWindow class or object. Redesign your architecture. There are many ways to achieve this, perhaps pass m_serial as a parameter to SendCommands::StartToSendCommand() so you can call write() on it.

[RuWex]

@JonB
so what should I do?

[JonB]

@RuWex
Mostly understand why creating a new MainWindow cannot be the right thing to do.

I have given you one simple suggested approach. Other ways might include (a) sending a signal from StartToSendCommand() with the character(s) to forward to the serial port or (b) move the serial port handling out of MainWindow into wherever suitable to be shared.

[RuWex]

@JonB
The truth is that I already did the idea you brought up and it caused the same problem:
sendCommand

void SendCommands::StartToSendCommand( QString fileName)//Ruth
{

        QFile file(fileName);
        if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
            return;

        QTextStream in(&file);
        QString line;
        while (!in.atEnd()) {
            line = in.readLine();
            for(int i=0; i< line.length(); ++i)
            {

                QString letter= (QString)line[i];

                QSerialPort *serial=mainSend->mainwind->SendCommand();
                serial->write(letter.toLatin1());
            }
            QApplication::processEvents();


        }

    }

MainWindow:

QSerialPort* MainWindow:: SendCommand()
{
    return m_serial;
}

[JonB]

@RuWex

QSerialPort *serial=mainSend->mainwind->SendCommand();

This does not correspond to any "idea you [I] brought up".
I do not know how you initialised mainSend->mainwind.
Since the error says "QIODevice::write (QSerialPort): device not open" presumably that tells you that whatever you are doing the QSerialPort *serial used in serial->write() is not open.

[RuWex]

@JonB said in I have an Error in my terminal :device not open- but usually it works...C++:

This does not correspond to any "idea you [I] brought up".
I do not know how you initialised mainSend->mainwind.
Since the error says "QIODevice::write (QSerialPort): device not open" presumably that tells you that whatever you are doing the QSerialPort *serial used in serial->write() is not open.

I forgot to upload another piece of code:

MainSendCommand:

MainSendCommand::MainSendCommand()
{
    sendCommand= new SendCommands();
    mainwind= new MainWindow();


}

I did it because I didnt want to do using mainWindow in Send Command file...
so what can be the problem?
I dont understand:(

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

so what can be the problem?
I dont understand:(

@JonB said in I have an Error in my terminal :device not open- but usually it works...C++:

@RuWex
Mostly understand why creating a new MainWindow cannot be the right thing to do.

I assume the mainwind= new MainWindow(); you show in MainSendCommand::MainSendCommand() is not the only MainWindow your application creates, and is not the MainWindow widget your application is actually showing. Until you understand the basics of C++ and what separate instances are you won't get very far.

I already suggested one of simpler alternatives is to pass m_serial (once opened!) to SendCommands or StartToSendCommand(). You have no need to be trying to access MainWindow from StartToSendCommand().

[RuWex]

@JonB
thank, you right I understand my mistake..:(
Im new to C++ so I dont still Master the material....
Do you have any Idea how to get the instance that already open?

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

Do you have any Idea how to get the instance that already open?

Like I said, do not try to pass or access the MainWindow instance you have created to MainSendCommand (or any other class). A good rule of thumb is do not allow yourself to go #include "mainwindow.h" in any file other than mainwindow.cpp, then you can never access it from elsewhere.

Assuming you create the MainSendCommand instance from your MainWindow (right?). So pass the serial port instance instead. Like maybe:

// Somewhere in `MainWindow`
mainSendCommand = new MainSendCommand(m_serial);

MainSendCommand::MainSendCommand(QSerialPort *serial)
{
    sendCommand= new SendCommands(serial);
}

SendCommands::SendCommands(QSerialPort *serial)
{
    this->m_serial = serial;
}

void SendCommands::StartToSendCommand( QString fileName)
{
    m_serial->write();
}

[RuWex]

@JonB
Wow I really appreciate it :)
But I didn't make an appearance of the class in mainSenfCommand, maybe I'll try to think of another idea in the style you suggested.
I have no words really thank you!!!

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

But I didn't make an appearance of the class in mainSenfCommand

I take that to mean "code does not create any instance of MainSendCommand"? Or do you create it somewhere? Else what is the point of having it? What does the MainSendCommand class do/add to your design? Maybe you don't need it and MainWindow should just create a SendCommands instance directly? This now all comes down to your overall program architecture.

[RuWex]

@JonB
I did it because I had a circular problem
sendCommand need function to mainwindow and mainwindow need function from send command
so I did more class that would solve the problem

[JonB]

@RuWex said in I have an Error in my terminal :device not open- but usually it works...C++:

sendCommand need function to mainwindow

Now that you know nothing should need or hold any reference to MainWindow maybe you can get rid of this MainSendCommand class and simplify.

[RuWex]

@JonB
yes, I think you right I have just now wanted to write it to you:)
thank!!!

[RuWex]

@JonB
I changed it as you said and it works well!!!