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boost::log::extract_or_default
// In header: <boost/log/attributes/value_extraction.hpp> template<typename T, typename TagT = void, typename DefaultT> result_of::extract_or_default< T, DefaultT, TagT >::type extract_or_default(attribute_name const & name, attribute_value_set const & attrs, DefaultT const & def_val);
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.
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Note |
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Caution must be exercised if the default value is a temporary object. Because the function returns a reference, if the temporary object is destroyed, the reference may become dangling. |
Parameters: |
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Returns: |
The extracted value, if found. The default value otherwise. |