template to retrieve QIODevice subclass

[onil]

Hi,
borisbn: I have tried your solution but still have 'no matching function for call to 'MyClass::device_cast(QIODevice*&)'

wysota: Yes I know that a function has to return a specific type. However I was hoping (and maybe I'm wrong) that using a template function I can have a function that returns SerialIODevice* when my QIODevice* is also a SerialIODevice*, a SslIODevice* when my QIODevice* is also a SslIODevice* and so on.
If none of the tested types are found, the default return type would be a QIODevice*.

What I exactly want is to store pointers to QIODevices in my class members in order to be able to use any class derived from QIODevice, BUT to call the subclass's functions when I make a call to memeber's functions (getChar, write, open, ...).

Regards.

[onil]

Hello everybody,

I have been very busy in the last couple of weeks so I left this problem aside. Yesterday I managed to solve my problem using the QMetaObject functionalities. See code example below to see how I managed to achieve my goal.

Thank you all for your help.

Regards.


myClass.h:

#ifndef MY_CLASS_H
#define MY_CLASS_H
 
#include <QObject>
#include <QThread>
#include <QIODevice>
 
class MyClass : public QThread
{
Q_OBJECT
 
public:
 
    explicit MyClass(QIODevice* inputDevice = 0, QObject *parent = 0);
    ~MyClass();
 
    void sendData(quint8 id, QByteArray data);
 
    some other members ...
 
private:
 
      QIODevice* m_pInputDevice;
      QIODevice* m_pForwardDevice;
 
      some other members ...
 
};
 
#endif // MY_CLASS_H

#ifndef MY_CLASS_H
#define MY_CLASS_H

#include <QObject>
#include <QThread>
#include <QIODevice>

class MyClass : public QThread
{
Q_OBJECT

public:

    explicit MyClass(QIODevice* inputDevice = 0, QObject *parent = 0);
    ~MyClass();

    void sendData(quint8 id, QByteArray data);

    some other members ...

private:

      QIODevice* m_pInputDevice;
      QIODevice* m_pForwardDevice;

      some other members ...

};
  
#endif // MY_CLASS_H

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myClass.cpp

#include "MyClass.h"
 
MyClass::MyClass(QIODevice* inputDevice, QObject *parent) :
    QThread(parent), m_pInputDevice(inputDevice), m_pForwardDevice(NULL), m_bForwardData(false)
{
}
 
MyClass::~MyClass()
{
    bool bRet;
        if(m_pInputDevice)
        {
            QMetaObject::invokeMethod(m_pInputDevice, "isOpen",
                                      Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
            if(bRet)
            {
                QMetaObject::invokeMethod(m_pInputDevice, "close",
                                          Qt::DirectConnection);
            }
        }
 
        if(m_pForwardDevice)
        {
            QMetaObject::invokeMethod(m_pForwardDevice, "isOpen",
                                      Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
            if(bRet)
            {
                QMetaObject::invokeMethod(m_pForwardDevice, "close",
                                          Qt::DirectConnection);
            }
    }
}
 
 // use case example
 
void MyClass::sendData(quint8 id, QByteArray data)
{
    bool bRet;
    if (!m_pInputDevice)
    {
        emit error("Input device not set!");
        return;
    }
 
    QMetaObject::invokeMethod(m_pInputDevice, "isOpen",
                              Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
    if(!bRet)
    {
        emit error("Input device is not open");
        return;
    }
 
    QFlags<QIODevice::OpenModeFlag> openMode;
    QMetaObject::invokeMethod(m_pInputDevice, "openMode",
                              Qt::DirectConnection, Q_RETURN_ARG(QFlags<QIODevice::OpenModeFlag>, openMode));
    if (openMode == QIODevice::ReadOnly)
    {
        emit error("Input device is in read only mode!");
        return;
    }
 
    // some processing...
 
    qint64 bytesWritten;
    QMetaObject::invokeMethod(m_pInputDevice, "write",
                              Qt::DirectConnection, Q_RETURN_ARG(qint64, bytesWritten), Q_ARG(QByteArray, data));
    if(bytesWritten == -1)
        emit error("Data output failed.");
}

#include "MyClass.h"

MyClass::MyClass(QIODevice* inputDevice, QObject *parent) :
    QThread(parent), m_pInputDevice(inputDevice), m_pForwardDevice(NULL), m_bForwardData(false)
{
}

MyClass::~MyClass()
{
    bool bRet;
        if(m_pInputDevice)
        {
            QMetaObject::invokeMethod(m_pInputDevice, "isOpen",
                                      Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
            if(bRet)
            {
                QMetaObject::invokeMethod(m_pInputDevice, "close",
                                          Qt::DirectConnection);
            }
        }

        if(m_pForwardDevice)
        {
            QMetaObject::invokeMethod(m_pForwardDevice, "isOpen",
                                      Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
            if(bRet)
            {
                QMetaObject::invokeMethod(m_pForwardDevice, "close",
                                          Qt::DirectConnection);
            }
    }
}

 // use case example

void MyClass::sendData(quint8 id, QByteArray data)
{
    bool bRet;
    if (!m_pInputDevice)
    {
        emit error("Input device not set!");
        return;
    }

    QMetaObject::invokeMethod(m_pInputDevice, "isOpen",
                              Qt::DirectConnection, Q_RETURN_ARG(bool, bRet));
    if(!bRet)
    {
        emit error("Input device is not open");
        return;
    }

    QFlags<QIODevice::OpenModeFlag> openMode;
    QMetaObject::invokeMethod(m_pInputDevice, "openMode",
                              Qt::DirectConnection, Q_RETURN_ARG(QFlags<QIODevice::OpenModeFlag>, openMode));
    if (openMode == QIODevice::ReadOnly)
    {
        emit error("Input device is in read only mode!");
        return;
    }

    // some processing...

    qint64 bytesWritten;
    QMetaObject::invokeMethod(m_pInputDevice, "write",
                              Qt::DirectConnection, Q_RETURN_ARG(qint64, bytesWritten), Q_ARG(QByteArray, data));
    if(bytesWritten == -1)
        emit error("Data output failed.");
}

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Example of SslIODevice

SslIODevice.h:

#ifndef SSL_IO_DEVICE_H
#define SSL_IO_DEVICE_H
 
#include <QSslSocket>
 
class SslIODevice : public QSslSocket
{
Q_OBJECT
 
public:
 
    explicit SslIODevice();
    ~SslIODevice();
 
    //For each QIODevice method I use
    Q_INVOKABLE [I]returnType[/I] method([I]args[/I]);
    some other members ...
 
private:
 
      some private members ...
 
};
 
#endif // SSL_IO_DEVICE_H

#ifndef SSL_IO_DEVICE_H
#define SSL_IO_DEVICE_H

#include <QSslSocket>

class SslIODevice : public QSslSocket
{
Q_OBJECT

public:

    explicit SslIODevice();
    ~SslIODevice();

    //For each QIODevice method I use
    Q_INVOKABLE [I]returnType[/I] method([I]args[/I]);
    some other members ...

private:

      some private members ...

};
  
#endif // SSL_IO_DEVICE_H

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SslIODevice.cpp

#include "SslIODevice.h"
 
SslIODevice::SslIODevice() :
    QSslSocket()
{
}
 
SslIODevice::~SslIODevice()
{
}
 
//For each QIODevice method I use
[I]returnType[/I] SslIODevice::method([I]args[/I])
{
    return QSslSocket::method([I]args[/I]);
}

#include "SslIODevice.h"

SslIODevice::SslIODevice() :
    QSslSocket()
{
}

SslIODevice::~SslIODevice()
{
}

//For each QIODevice method I use
[I]returnType[/I] SslIODevice::method([I]args[/I])
{
    return QSslSocket::method([I]args[/I]);
}

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