Re: [Cppcms-users] C++ locale and boost.locale

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

> 
> BTW, thanks to your help, I got the  missing piece, so that I finally managed 
>to 
>
> do what I wanted to  do:
> 
> #include <sstream>
> #include  <boost/locale.hpp>
> 
> std::string timestamp_to_string(time_t  const& tt) {
>         using namespace  boost::locale;
>         generator gen;
>          std::locale::global(gen("en_US.UTF-8"));
>          std::stringstream ss;
>          ss.imbue(std::locale());
>         ss << as::date  << tt << " ";
>         ss << as::time  << tt << std::endl;
>         std::string r =  "";
>         getline(ss, r);
>          return r;
> }
> 

Few points:

> timestamp_to_string(time_t  const& tt) 

It is better to write

   timestamp_to_string(time_t tt) 

As time_t is integral type and it is better
to pass it by value.

>         using namespace  boost::locale;
>         generator gen;
>          std::locale::global(gen("en_US.UTF-8"));
>          ss.imbue(std::locale());


Is very inefficient as locale generation is very
heavy procedure.

In CppCMS context you have this member function:

http://cppcms.sourceforge.net/cppcms_ref_v0_99/classcppcms_1_1http_1_1context.html#39fde738210daf84deee691f45260e5b


So basically inside cppcms::application based class just write

  std::locale loc = context().locale();

or

  std::locale loc = context().locale("en_US.UTF-8");

It returns the locale defined in configuration file for you
and it would cache the locale automatically for future use.

>          std::locale::global(gen("en_US.UTF-8"));
>          ss.imbue(std::locale());


Even if you use it, it is better to write

    ss.imbue(gen("en_US.UTF-8"));

And not set global locale and then create a locale
instance from global one.

>         ss << as::date  << tt << " ";
>         ss << as::time  << tt << std::endl;

It is better to write

   ss << as::datetime << tt;

>         std::string r =  "";

r is empty by default, no need r="";

>         getline(ss, r);
>          return r;

It is better to call

   return ss.str()

Of course without "<<std::endl"




> It took me 10-20 hours to research, read and  understand enough to come up with 
>
> the seemingly simple piece of code above.  :-/ 
> 
> I use it to format unix timestamps before pushing it to my 
> cppcms::base_content object.
> 
> I don't know if it's the right approach,  but it works...
> 

It is much simpler, you have filers namespace

  http://cppcms.sourceforge.net/cppcms_ref_v0_99/namespacecppcms_1_1filters.html

So just write in the template


   <% tt | datetime %> 

Or even with more fine grained control

   <% tt | strftime("%Y-%m-%d %H:%M:%S %Z") %> 


where tt is just time_t in your context :-)

> 
> 
> Augustin.


Best,
  Artyom