Implement support for connecting void-args functions on Events. The use case is to shorten the function signature in cases where the user does not care about the event arguments.

include/Event.h

@@ -39,6 +39,14 @@ public:
     Connection Connect(delegate callback);
     void Disconnect(Connection &conn);
     Connection operator+=(delegate callback);
+
+    /// Also support binding callbacks that don't read in arguments, as a shorthand.
+    // TODO: No need to wrap the callback if the template args type is void.
+    Connection Connect(const std::function<void()>& default_callback);
+    /// Also support binding callbacks that don't read in arguments, as a shorthand.
+    // TODO: No need to wrap the callback if the template args type is void.
+    Connection operator += (const std::function<void()>& default_callback);
+
 protected:
     std::vector<EventPtr> listeners;
 };
@@ -62,6 +70,19 @@ bool BasicEvent<delegate, Args...>::Connection::Disconnect() {
 template<typename delegate, typename... Args>
 BasicEvent<delegate, Args...>::Connection BasicEvent<delegate, Args...>::operator+=(delegate callback) { return Connect(callback); }
 
+template<typename delegate, typename ... Args>
+typename BasicEvent<delegate, Args...>::Connection BasicEvent<delegate, Args...>::Connect(
+    const std::function<void()> &default_callback) {
+    delegate wrapper = [default_callback] (Args... args) { default_callback(); };
+    return Connect(wrapper);
+}
+
+template<typename delegate, typename ... Args>
+typename BasicEvent<delegate, Args...>::Connection BasicEvent<delegate, Args...>::operator+=(
+    const std::function<void()> &default_callback) {
+    return Connect(default_callback);
+}
+
 template<typename delegate, typename... Args>
 void BasicEvent<delegate, Args...>::operator()(Args... args) { Invoke(args...); }
 

main.cpp

@@ -24,6 +24,10 @@ int main() {
     };
     auto handler2 = OnMessage += ProcessMessage;
 
+    auto handler3 = OnMessage += [&] {
+        std::cout << "Connect to event, with default callback, if we don't care about using the provided arguments." << std::endl;
+    };
+
     while (run)
     {
         std::string input;