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POHow to make a C++ boost::signal be caught from an object which encapsulates the object which emits it?
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copied!<p>I have a <strong>TcpDevice</strong> class which encapsulates a TCP connection, which has an <em>onRemoteDisconnect</em> method which gets called whenever the remote end hangs up. Then, there's a <strong>SessionManager</strong> object which creates <strong>TcpSession</strong> objects which take a <strong>TcpDevice</strong> as a communication channel and inserts them in an internal pointer container for the application to use. In case any of the managed <strong>TcpSessions</strong> should end, I would like the <strong>SessionManager</strong> instance to be notified about it and then remove the corresponding session from the container, freeing up the resources associated with it.</p> <p>I found my problem to be very similar to this question:</p> <p><a href="https://stackoverflow.com/q/862093/1007502">Object delete itself from container</a></p> <p>but since he has a thread for checking the connections state, it gets a little different from mine and the way I intended to solve it using <em>boost::signals</em>, so I decided to go for a new question geared towards it - I apologize if it's the wrong way to do it... I'm still getting the feel on how to properly use S.O. :)</p> <p>Since I'm kind of familiar with QT signals/slots, I found <strong>boost::signals</strong> offers a similar mechanism (I'm already using <em>boost::asio</em> and have no QT in this project), so I decided to implement a <strong><em>remoteDeviceDisconnected</em></strong> signal to be emitted by <strong>TcpDevice's</strong> <em>onRemoteDisconnect</em>, and for which I would have a slot in <strong>SessionManager</strong>, which would then delete the disconnected session and device from the container.</p> <p>To initially try it out I declared the signal as a public member of <strong>TcpDevice</strong> in <em>tcpdevice.hpp</em>:</p> <pre><code>class TcpDevice { (...) public: boost::signal <void ()> remoteDeviceDisconnected; (...) } </code></pre> <p>Then I emitted it from <strong>TcpDevice's</strong> <em>onRemoteDisconnect</em> method like this:</p> <pre><code>remoteDeviceDisconnected(); </code></pre> <p>Now, is there any way to connect this signal to my <strong>SessionManager</strong> slot from <strong><em>inside</em></strong> session manager? I tried this:</p> <pre><code>unsigned int SessionManager::createSession(TcpDevice* device) { unsigned int session_id = session_counter++; boost::mutex::scoped_lock lock(sessions_mutex); sessions.push_back(new TcpSession(device, session_id)); device->remoteDeviceDisconnected.connect(boost::bind(&SessionManager::removeDeadSessionSlot, this)); return session_id; } </code></pre> <p>It compiles fine but at link time it complains of multiple definitions of <em>remoteDeviceDisconnected</em> in several object code files:</p> <pre><code>tcpsession.cpp.o:(.bss+0x0): multiple definition of `remoteDeviceDisconnected' tcpdevice.cpp.o: (.bss+0x0): first defined here sessionmanager.cpp.o:(.bss+0x0): multiple definition of `remoteDeviceDisconnected' tcpdevice.cpp.o: (.bss+0x0): first defined here </code></pre> <p>I found this strange, since I didn't redefine the signal anywhere, but just used it at the <em>createSession</em> method above.</p> <p>Any tips would be greatly appreciated! Thank you!</p>

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