Jpelkey: New page: {{TOC}} Sometimes the API in use may require a callback; however, for your particular function, you may not wish to provide one. In this case, it is possible to provide a null callback. ...

2009-05-22T13:35:46Z

New page: {{TOC}} Sometimes the API in use may require a callback; however, for your particular function, you may not wish to provide one. In this case, it is possible to provide a null callback. ...

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Sometimes the API in use may require a callback; however, for your particular function, you may not wish to provide one. In this case, it is possible to provide a null callback.

== HOWTO use null callbacks ==

To use a null callback, use the ns3::MakeNullCallback construct:

template<typename R>
Callback< R, T1, T2, T3, T4, T5, T6 > ns3::MakeNullCallback (void)

Example usage: The ns3::Socket class uses callbacks to indicate completion of events such as a successful TCP connect(). These callbacks are set in the following function:

void Socket::SetConnectCallback (Callback<void, Ptr<Socket> > connectionSucceeded,
Callback<void, Ptr<Socket> > connectionFailed,
Callback<void, Ptr<Socket> > halfClose);

But suppose you do not care about registering a callback for the halfClose event (but you want to register one for the connectionSucceeded and connectionFailed cases). In that case, you can pass a null callback as the third argument. You just need to pass a callback with the matching signature, as follows:

localSocket->SetConnectCallback (
MakeCallback (&ConnectionSucceededCallback),
MakeCallback (&ConnectionFailedCallback),
MakeNullCallback<void, Ptr<Socket> > () );

HOWTO use null callbacks - Revision history

Jpelkey: New page: {{TOC}} Sometimes the API in use may require a callback; however, for your particular function, you may not wish to provide one. In this case, it is possible to provide a null callback. ...