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Struct template attribute_keyword

boost::log::expressions::attribute_keyword — This class implements an expression template keyword.

Synopsis

// In header: <boost/log/expressions/keyword_fwd.hpp>

template<typename DescriptorT, template< typename > class ActorT> 
struct attribute_keyword {

  // public static functions
  static attribute_name get_name();
  static or_none_result_type or_none();
  static or_throw_result_type or_throw();
  template<typename DefaultT> 
    static attribute_actor< value_type, fallback_to_default< DefaultT >, descriptor_type, ActorT > 
    or_default(DefaultT const &);
};

Description

This class implements an expression template keyword. It is used to start template expressions involving attribute values.

`attribute_keyword` public static functions

```
static attribute_name get_name();
```
Returns attribute name.
```
static or_none_result_type or_none();
```
Generates an expression that extracts the attribute value or a default value.
```
static or_throw_result_type or_throw();
```
Generates an expression that extracts the attribute value or throws an exception.

template<typename DefaultT> 
  static attribute_actor< value_type, fallback_to_default< DefaultT >, descriptor_type, ActorT > 
  or_default(DefaultT const & def_val);

Generates an expression that extracts the attribute value or a default value.