Re: [Boost-users] How to use the optional with property_tree‏

Subject: Re: [Boost-users] How to use the optional with property_tree‏
From: 王郁槐 (wyhfly_at_[hidden])
Date: 2013-12-19 09:28:13

I still don't understand，could you please figure it out？thanks.


发送自魅族手机

-------- 原始邮件 --------
发件人：Olivier Tristan <[e-mail]>
时间：周四 12月19日 22:08
收件人：[e-mail]
主题：Re: [Boost-users] How to use the optional with property_tree‏

Those following lines from your code should give you a hint

if (child2)
{
child2.get().put_value(strValue);
}
else
{
child2.get().put_value(strValue);
}

      
      
      Le 19/12/2013 12:34, 王郁槐 a écrit :
> Could anyone help? Why the below code will crash on the below line? I'm using the boost property_tree. Thanks.
>
> child1.get().put(sub_field, strValue);
>
> =========================================================
> #include <fstream>
> #include <boost/filesystem.hpp>
> #include <boost/property_tree/ptree.hpp>
> #include <boost/property_tree/ini_parser.hpp>
> #include <boost/any.hpp>
> #include <boost/optional.hpp>
>
> void writeConfig(const std::string &field, const std::string &sub_field, const std::string & strValue)
> {	
> if (!boost::filesystem::exists(prog_cfg_file))
> {
> std::ofstream ofIniConfig(prog_cfg_file, std::ofstream::out|std::ofstream::app);
> ofIniConfig.close();
> }
>
>
> boost::property_tree::ptree pt;
> boost::property_tree::ini_parser::read_ini(prog_cfg_file, pt);	
> boost::optional<boost::property_tree::ptree&> child1 = pt.get_child_optional(field);
>
> if (child1)
> {
> boost::optional<boost::property_tree::ptree&> child2 = child1.get().get_child_optional(sub_field);
>
> if (child2)
> {
> child2.get().put_value(strValue);
> }else
> {
> child2.get().put_value(strValue);
> }
> }else
> {
> child1.get().put(sub_field, strValue);
> }
>
> boost::property_tree::ini_parser::write_ini(prog_cfg_file, pt);
> }
>
> int main()
> {
> writeConfig("test", "a", "OK");
> return 0;
> } 
>         
>         
>         
>         
> --
> 兰生幽谷, 不以无人而不芳...
>       
>       
>       
>       
> _______________________________________________
> Boost-users mailing list
> [e-mail]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>     
    
    
-- 
      Olivier TRISTAN
      uvi.net

I still don't understand，could you please figure it out？thanks.

发送自魅族手机

-------- 原始邮件 --------
发件人：Olivier Tristan <o.tristan_at_[hidden]>
时间：周四 12月19日 22:08
收件人：boost-users_at_[hidden]
主题：Re: [Boost-users] How to use the optional with property_tree‏

>Those following lines from your code should give you a hint
>
>if (child2)
>{
>child2.get().put_value(strValue);
>}
>else
>{
>child2.get().put_value(strValue);
>}
>
>
>
>Le 19/12/2013 12:34, 王郁槐 a écrit :
>> Could anyone help? Why the below code will crash on the below line? I'm using the boost property_tree. Thanks.
>>
>> child1.get().put(sub_field, strValue);
>>
>> =========================================================
>> #include <fstream>
>> #include <boost/filesystem.hpp>
>> #include <boost/property_tree/ptree.hpp>
>> #include <boost/property_tree/ini_parser.hpp>
>> #include <boost/any.hpp>
>> #include <boost/optional.hpp>
>>
>> void writeConfig(const std::string &field, const std::string &sub_field, const std::string & strValue)
>> {	
>> if (!boost::filesystem::exists(prog_cfg_file))
>> {
>> std::ofstream ofIniConfig(prog_cfg_file, std::ofstream::out|std::ofstream::app);
>> ofIniConfig.close();
>> }
>>
>>
>> boost::property_tree::ptree pt;
>> boost::property_tree::ini_parser::read_ini(prog_cfg_file, pt);	
>> boost::optional<boost::property_tree::ptree&> child1 = pt.get_child_optional(field);
>>
>> if (child1)
>> {
>> boost::optional<boost::property_tree::ptree&> child2 = child1.get().get_child_optional(sub_field);
>>
>> if (child2)
>> {
>> child2.get().put_value(strValue);
>> }else
>> {
>> child2.get().put_value(strValue);
>> }
>> }else
>> {
>> child1.get().put(sub_field, strValue);
>> }
>>
>> boost::property_tree::ini_parser::write_ini(prog_cfg_file, pt);
>> }
>>
>> int main()
>> {
>> writeConfig("test", "a", "OK");
>> return 0;
>> }
>>
>>
>>
>>
>> --
>> 兰生幽谷, ä¸ä»¥æ— äººè€Œä¸èŠ³...
>>
>>
>>
>>
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>
>
>-- 
>Olivier TRISTAN
>uvi.net
>
>_______________________________________________
>Boost-users mailing list
>Boost-users_at_[hidden]
>http://lists.boost.org/mailman/listinfo.cgi/boost-users