Avoid dynamic_cast with derived classes (Cast Derived class)

Question

I am new to C++ and came to a point, where I generate an overhead with classes. I have a QTcpSocket and read messages from it and create objects, for example MessageJoin, Me

Answer 1

The visitor pattern could be a good fit i.e.

class Message
{
public:
    QString virtual getRawMessage() { return dataRawMessage; }

    virtual void accept(Client& visitor) = 0;

protected:
    QString dataRawMessage;
};

// Join class - cointains the name of the joined user and the channel
class MessageJoin : public Message
{
public:
    MessageJoin(const QString &rawmessage, const QString &channel, const QString &user)
    {
        dataRawMessage = rawmessage;
        dataChannel = channel;
        dataUser = user;
    }

    QString getChannel() { return dataChannel; }
    QString getUser(){ return dataUser; }

    void accept(Client& visitor) override
    {
          visitor.visit(*this);
    }

private:
    QString dataChannel;
    QString dataUser;
};

// Notice class - contains a notification message
class MessageNotice : public Message
{
public:
    MessageNotice(const QString &rawmessage, const QString &text)
    {
        dataRawMessage = rawmessage;
        dataText = text;
    }

    QString getText() { return dataText;}

    void accept(Client& visitor) override
    {
          visitor.visit(*this);
    }

private:
    QString dataText;
};

void Client::visit(MessageJoin& msg)
{
    qDebug() << msg.getUser() << " joined " << msg.getChannel();
    // Update UI: Add user
}

void Client::visit(MessageNotice& msg)
{
    qDebug() << msg.getText();
    // Update UI: Display message
}

// Client code - print message and update UI
void Client::messageReceived(Message *message)
{
    if(message)
    {
        message->visit(this);
        delete message; // Message was allocated in the library and is not used anymore
    }
}