C++中的多类型容器

Multi-type container in C++

本文关键字:多类型 C++      更新时间:2023-10-16

我正在寻找一个C++类来存储要用作全局配置机制的多类型参数。

以下近似值存储了param_name - param_value对。其中参数值为多类型。

有人知道为此目的的任何图书馆或替代方案吗?

以下代码有什么替代方法吗?

#ifndef _GLOBAL_CONFIG_HPP_
#define _GLOBAL_CONFIG_HPP_
#include <boost/any.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/optional/optional.hpp>
#include <map>
#include <string>
#include <ostream>
#include <typeinfo>
namespace GC
{
  class Global_Config
  {
  public:
    typedef std::string label_t;
    typedef std::map< label_t, boost::any > data_m_t;
  private:
    data_m_t data_m_;
  public:
    template< class T >
    void get( boost::optional< T >& data, const label_t& label )
      throw (  boost::bad_any_cast, std::bad_alloc )
    {
      data_m_t :: iterator it = data_m_.find( label );
      data = ( it == data_m_.end( ) ) ?
             boost::optional< T >( ) : boost::any_cast< T >( it->second );
    }
    template< class T >
    void set( const label_t& label, const T& data )
    {
      data_m_[ label ] = data;
    }
    friend std::ostream& operator<< ( std::ostream& os, const Global_Config& gc );
  };

  class ex_chk_type_ok : public std::exception { };
  // WARNING: throwing ex when type found for performance purposes!!!!
  template< class T >
  void ostream_over_global_config_chk_type( std::ostream& os,
                        const boost::any& value)
  {
    if( value.type( ) == typeid( T ) )
    {
     os << boost::any_cast< T > ( value );
     throw ex_chk_type_ok( ); 
    }
  }

  std::ostream& operator<<( std::ostream& os, const Global_Config& gc )
  {
    for( Global_Config::data_m_t:: const_iterator it( gc.data_m_.begin( ) );
     it != gc.data_m_.end( ); ++it )
     {
      os << it->first <<  ("=");
      try 
      {
        ostream_over_global_config_chk_type< bool >              ( os, it->second );
        ostream_over_global_config_chk_type< char >              ( os, it->second );
        ostream_over_global_config_chk_type< short >             ( os, it->second );
        ostream_over_global_config_chk_type< unsigned short>     ( os, it->second );
        ostream_over_global_config_chk_type< int >               ( os, it->second );
        ostream_over_global_config_chk_type< unsigned int>       ( os, it->second );
        ostream_over_global_config_chk_type< float >             ( os, it->second );
        ostream_over_global_config_chk_type< long>               ( os, it->second );
        ostream_over_global_config_chk_type< unsigned long >     ( os, it->second );
        ostream_over_global_config_chk_type< long long >         ( os, it->second );
        ostream_over_global_config_chk_type< unsigned long long >( os, it->second );
        ostream_over_global_config_chk_type< double >            ( os, it->second );
        ostream_over_global_config_chk_type< long double >       ( os, it->second );
        ostream_over_global_config_chk_type< wchar_t >           ( os, it->second );
        ostream_over_global_config_chk_type< std::string >       ( os, it->second );
      } catch(  ex_chk_type_ok &ex )
      {
        //Do nothing, ex to break checkings for performance purposes...
      }
      os << "(" << it->second.type( ).name( ) << ")";
      if( it != gc.data_m_.end( ) ) os << ";";
    }
    return os;  
  }
}; // ns GC
#endif

最动态的配置方式是 Poco::D ynamicAny 行。

这就像任何一样,但在检索值时不需要强制转换。给定一个DynamicAny的对象,你可以做:

DynamicAny d{100.2};
//Note that there is no need for casting
double my_double = d;

配置的另一种选择是Boost.Program_Options,我认为这主要用于命令行,但也可用于从文件,如果我记错了。Boost.PropertyTree.主要用于分层配置文件。