On Tuesday 26 July 2005 22:45, Rebooted wrote:
In my program I need to store a map of signals, with an integer id corresponding to a signal in the map.
Some kind of map<id_type, signal_type>.
Objects can request to be informed when another a specific message is emitted by connecting a member function to the signal in this map at the index corresponding to that message type.
IOW, objects can subscribe to events.
However, since boost::signal inherits noncopyable, it cannot be stored in a map. What are the reasons for signal being noncopyable, and is there any chance this could be changed in the future?
(I'm walking on unknown grounds here, since I use libsigC++ instead, but last time I looked, they were sufficiently similar - maybe some names are different.) The problem is that when you connect a slot to a signal, you get a reference to that connection. Using that reference, you can also separate the connection again. Now, what would happen when a signal was copyable? You could end up with several connections, so which one would you disconnect? Also, copying is not a trivial operation, so you'd rather avoid it. Ideas: Use Boost's function instead, which is copyable. Using bind, you can achieve almost the same as with slots/signals. The exception is the automatic disconnecting when the target object is destroyed, but that can also be achieved by using weak_ptr and a wrapper function (maybe lambda would eliminate even that). Store a smart pointer instead of the signal itself. This would even speed up operations on the map. Uli