QTcpServer copy constructor

nevdokimof

Why the copy constructor of QTcpServer is private?

So instead of this:

//server.h

class Server : public QObject
{
    Q_OBJECT

private:
    QTcpServer tcpServer;

public:
    explicit Server(QObject *parent = nullptr);
};

//server.cpp

Server::Server(QObject *parent) : QObject(parent)
{
    tcpServer = QTcpServer();
}

I am forced to use pointer to an object, like this:

//server.h

class Server : public QObject
{
    Q_OBJECT

private:
    QTcpServer* tcpServer;

public:
    explicit Server(QObject *parent = nullptr);
};

//server.cpp

Server::Server(QObject *parent) : QObject(parent)
{
    tcpServer = new QTcpServer();
}

I believe it is not memory safe, am I wrong?

Christian Ehrlicher

You just have to make sure to delete the pointer when it is no longer needed (e.g. in the dtor).
Or pass a valid parent so it gets automatically deleted when the parent is deleted - see http://doc.qt.io/qt-5/objecttrees.html

nevdokimof

Oh, so I can set this (in my case) as a parent of my tcpServer and it will be automatically destroyed with the Server destruction?

Seems a bit tricky

mrjj

@nevdokimof
Whole Qt is designed about this system.
Its works really well and free you from the burden of deleting all the widgets manually.
The reason the copy constructor is disabled is that you are not allowed to clone most Qt objects
due to identity and the signal and slot system.
Its all explained in the link mr @Christian-Ehrlicher shows.

VRonin

Hi, just a side note, it is perfectly valid to allocate a QObject on the stack.

class Server : public QObject
{
    Q_OBJECT

private:
    QTcpServer tcpServer;

public:
    explicit Server(QObject *parent = nullptr);
};
Server::Server(QObject *parent) : QObject(parent){}

is perfectly fine.
What you are having trouble with is tcpServer = QTcpServer(); which is unnecessary in C++. If you need to pass arguments to the constructors of your QObjects you can do it via the initializer list