Re: [Cppcms-users] Design decision

[Artyom B. <art...@ya...>]

Just few words,

booster::aio::io_service::post is 
used to execute something in the event loop
"later" i.e. you give a callback and it would
executed in the dispatch queue of the event
loop, it is also important that it is thread safe.

Post used for two reasons:

1. Make sure that the handler is not called right now but
   rather put into queue - it is very useful to
   prevent accidential recursions

2. When you need to execute something on non-thread safe class
   withing the event loop thread, as post is thread safe.

   i.e. if some event driven object like asyncrchonous app.,
   aio socket etc. runs withing the event loop and you want to
   for example send something to socket form another thread,
   you can't do it directly as socket objects, application
   objects are not thread safe, so you POST the callback
   and you know that it would be called in the event loop
   rather than the thread


In your case the callback of the "on_readable()" is already
called from the event loop, so you don't really need to
post() anything as you are already in the event loop,

As SSE::handle should be called from the event loop and you
are in the event loop the callback of  "on_readable()"
than instead:

  this->get_io_service().post(std::bind(&SSE::handle,this,....)

You just call

  handle(something,ip) ...

If you still want to post() (you can but not have to), once again, lambda:

  this->get_io_service().post([=,this]() { 
    handler(something,ip)
  });

How to do it with bind? As I said before read :

   http://www.boost.org/doc/libs/1_51_0/libs/bind/bind.html



 
Artyom Beilis
--------------
CppCMS - C++ Web Framework:   http://cppcms.com/
CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/



----- Original Message -----
> From: Christian Gmeiner <chr...@gm...>
> 
> I have looked quite deeply into post(..) usages, but I don't get it :/
> I have seen binder's -
> what is the concept behind them?
> 
> thanks
> ---
> Christian Gmeiner MSc
>