Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Function template extract

boost::log::extract

Synopsis

// In header: <boost/log/attributes/value_extraction.hpp>


template<typename DescriptorT, template< typename > class ActorT> 
  result_of::extract< typenameDescriptorT::value_type, DescriptorT >::type 
  extract(expressions::attribute_keyword< DescriptorT, ActorT > const & keyword, 
          record const & rec);

Description

The function extracts an attribute value from the view. The user has to explicitly specify the type or set of possible types of the attribute value to be extracted.

Parameters:

`keyword`	The keyword of the attribute value to extract.
`rec`	A log record. The attribute value will be sought among those associated with the record.

Returns:

A value_ref that refers to the extracted value, if found. An empty value otherwise.