Re: [Boost-users] Need boost's help with poor design

On Thu, Mar 27, 2008 at 11:30 AM, Steven Watanabe wrote:

AMDG

Robert Dailey wrote:

...

It's sad to find out about the restrictions of the templates, but I can understand. I just finally began to understand your design proposal and had already planned on using it :(

Well, you could use MPL list which does not have a fixed upper limit, but you may just run into compiler limits instead of MPL limits.

...

Your unordered_map seems redundant, in that you have packet ID's to different function objects with exactly the same signature. I guess this is so we only dispatch packets to subscribers interested in that specific packet. Could you emphasize a little more on what you mean by "store references to the individual signals"? The downcasting logic could be done via a 'get' method.... packet::get<WalkPacket>(), but this is pretty much exactly like doing static_cast<>() directly. get() would have the potential of returning a NULL auto_ptr if the type specified by the get<>() does not represent the concrete type of the packet.

typedef boost::unordered_map > dispatcher;

template<class T> struct StaticCaster { StaticCaster(boost::signal &signal) : signal(signal) {} boost::signal &signal; void operator()(Packet const& packet) const { signal(static_cast(packet)); } };

// load the table. // you will probably need a second map to allow functions to // be registered with the signals.

boost::signal walkPacketSignal; dispatcher.insert(make_pair(PID_WALKPACKET, staticCaster<WalkPacket>(walkPacketSignal)));

// dispatching

dispatcher[id](packet);

In Christ, Steven Watanabe

I didn't find any documentation on unordered_map in the boost documentation. What's the reason for not sorting the map? It seems like it would be more inefficient. STL Map is sorted for a reason. BTW thank you for the design here. Can't believe I didn't think about this :)