[asio] Correct handler signature for io_service::post/dispatch
Currently I'm developing a server that uses Boost.Asio, version 1.49. It makes use of io_service::post and io_service::dispatch to invoke handlers running in the same process, but on different threads. Some of the handlers invoke a function with the following signature: void handler(std::string s); This works fine and no problems have been observed. However, subsequently I read in the asio documentation that the function signature of a handler invoked by post/dispatch *must* be in the following format: void handler(); Is my code working by chance or is the asio version 1.49 documentation out of date? Regards Gary Sanders
Currently I'm developing a server that uses Boost.Asio, version 1.49. It makes use of io_service::post and io_service::dispatch to invoke handlers running in the same process, but on different threads. Some of the handlers invoke a function with the following signature:
void handler(std::string s);
This works fine and no problems have been observed. However, subsequently I read in the asio documentation that the function signature of a handler invoked by post/dispatch *must* be in the following format:
void handler();
Is my code working by chance or is the asio version 1.49 documentation out of date?
io_service::post() accepts nullary functors. So if your handler accept parameters, I guess you bind them at when posting the handler, don't you.
On 20/05/2012 16:08, Igor R wrote:
Currently I'm developing a server that uses Boost.Asio, version 1.49. It makes use of io_service::post and io_service::dispatch to invoke handlers running in the same process, but on different threads. Some of the handlers invoke a function with the following signature:
void handler(std::string s);
This works fine and no problems have been observed. However, subsequently I read in the asio documentation that the function signature of a handler invoked by post/dispatch *must* be in the following format:
void handler();
Is my code working by chance or is the asio version 1.49 documentation out of date?
io_service::post() accepts nullary functors. So if your handler accept parameters, I guess you bind them at when posting the handler, don't you. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Yes, this is the sort of thing that I'm doing and that I find to be working OK. ios.post(boost::bind(&MyClass::Handler,ptr_to_my_class,"astring")); So, this is OK?
io_service::post() accepts nullary functors. So if your handler accept parameters, I guess you bind them at when posting the handler, don't you.
Yes, this is the sort of thing that I'm doing and that I find to be working OK.
ios.post(boost::bind(&MyClass::Handler,ptr_to_my_class,"astring"));
So, this is OK?
Yes, of course.
On Sun, May 20, 2012 at 04:52:41PM +0100, Gary Sanders wrote:
On 20/05/2012 16:08, Igor R wrote:
Currently I'm developing a server that uses Boost.Asio, version 1.49. It makes use of io_service::post and io_service::dispatch to invoke handlers running in the same process, but on different threads. Some of the handlers invoke a function with the following signature:
void handler(std::string s);
This works fine and no problems have been observed. However, subsequently I read in the asio documentation that the function signature of a handler invoked by post/dispatch *must* be in the following format:
void handler();
io_service::post() accepts nullary functors. So if your handler accept parameters, I guess you bind them at when posting the handler, don't you. _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users
Yes, this is the sort of thing that I'm doing and that I find to be working OK.
ios.post(boost::bind(&MyClass::Handler,ptr_to_my_class,"astring"));
So, this is OK?
The result of the bind call is an object of a type that overloads operator () with suitable parameters. Unless the recipient is aware of the undocumented return type of Bind, all it sees is a callable object. As Igor said, post accepts anything that is callable with the signature "void ()". This includes the result of your bind expression, a free function pointer with no parameters, an user-defined class with overloaded nullary operator(), etc. In this case, you have no placeholders, so it's invokable with any set of parameters (unused arguments are ignored), so it satisfies the requirements that post() have. If you tried to do something like this, you'd fail miserably as you do not honor the contract on the parameter for Post: void f(std::string s); ios.post(&f); -- Lars Viklund | zao@acc.umu.se
participants (2)
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Gary Sanders -
Igor R -
Lars Viklund