Re: [Boost-users] [program_options] call notify() twice?

From: Marty Fried (public.forums_at_[hidden])
Date: 2008-06-26 11:54:35

Back on Wed, 25 Jun 2008 09:47:16 +0400, in
gmane.comp.lib.boost.user,Vladimir Prus <vladimir_at_[hidden]> wrote:

>Marty Fried wrote:
>
>> My app has a configuration file. We don't know where it will be for sure, so
>> we are planning to make the location of the file a commandline option.
>> 
>> So, after reading the commandline option, we will want to parse the config
>> file.
>> 
>You don't need to call 'notify' twice -- first, parse the command line (including
>calling 'store' put the option into variables_map). Obtain the value of the
>necessary option from the variables map, and if necessary, parse the
>config file, again, including 'store' like:
>
>        store(parse_config_file(ifs, config_file_options), vm);
>
>After that, call 'notify(vm)' -- once.

Thanks a lot; I didn't know the purpose of notify, and thought it might be
necessary to get the data into the variables_map.  This way makes sense to
me, now.
>
>I don't think that anything will break *now*, if you call notify twice, but then, 
>the documentation say:
>
>   /** Specifies a function to be called when the final value
>            is determined. */
>   typed_value* notifier(function1<void, const T&> f)
>
>and reporting the *final* value twice seems weird.
>
That's the reason I didn't want to simply try it and assume the result is
the design.  

Far be it for me to do something weird. :-)

Thanks for your input.
-- 
Marty Fried  
Senior software engineer 
Aldon  http://www.aldon.com