Hello. I'm having problems with boost::signal. I have a simple callback system: typedef boost::signal<void (const String &)> StringCallbacks; TSharedPtr<StringCallbacks> stringCallbacks; stringCallbacks contains void (Const String &) -callback functions. New callback functions are registered into the callback system with registerCallback -function: template<class VarType> class SettingUpdater { private: VarType & reference; SettingUpdater(VarType & var) : reference(var) { } public: void operator()(const String & setting) { // do someting irrelevant for the question here // with the reference -variable } }; boost::signals::connection registerCallback(StringCallbacks::slot_type callback) { // PROBLEM: I'd like to call the callback once without calling every callback // which are possibly registered already into the signal before this. // Register the new callback into the signal. return stringCallbacks.get()->connect(callback); } The actual usage of registerCallback: int localVariable; registerCallback(SettingUpdater<int>(localVariable)); Question: As you might already see above, I'd like to call the callback function once in the registerCallback function without calling every callback already registered in the stringCallbacks signal. I first tried something like String param = "foo"; callback(param); but that won't compile. I also tried callback.get_slot_function()(param); That compiles, but it won't execute the operator() -function in SettingUpdater. Calling the signal will execute all callbacks registered, so the SettingUpdater function seems working. How I can execute the operator() function in SettingUpdater<> inside registerCallback function by the callback parameter passed to registerCallback function? Thanks in advance =) - Juho Mäkinen