Dear Boost experts!
I'm new to this list, so please have mercy if I'm not yet familiar with
your best practices.
Recently, I have been pulling my hair out while trying to use boost::log
for a severity-logger-type functionality where the sink backend is not
compatible with std::ostream. Best bet was to implement a custom sink
backend that does the job in its consume() member.
However, I can't get the attribute value for the severity level
extracted to an int. For sure, there's something totally obvious I'm
missing... Here's the source code (slightly abbreviated):
#include <string>
#include
#include
#include
#include
#include
#include
#include
#include
#include
namespace logging = boost::log;
namespace sinks = boost::log::sinks;
void SomeLogChannel(int severity, const std::string& message) {}
class SinkBackend : public sinks::basic_sink_backendsinks::synchronized_feeding
{
public:
explicit SinkBackend() {}
void consume(logging::record_view const& rec)
{
std::string message = *rec[boost::log::expressions::smessage];
int severity = 0;
if (rec.attribute_values().count("Severity"))
{
// severity = rec.attribute_values()["Severity"].extract<int>(); // cannot convert from 'boost::log::v2s_mt_nt6::value_ref' to 'int' with T=int, TagT=void
}
SomeLogChannel(severity, message);
}
};
void init_logging()
{
typedef sinks::synchronous_sink<SinkBackend> sink_t;
boost::shared_ptrlogging::core core = logging::core::get();
boost::shared_ptr<SinkBackend> backend(new SinkBackend());
boost::shared_ptr sink(new sink_t(backend));
core->add_sink(sink);
core->set_filter(logging::trivial::severity >= logging::trivial::error);
}
int main(int, char* [])
{
init_logging();
boost::log::sources::severity_logger< logging::trivial::severity_level > lg;
BOOST_LOG_SEV(lg, logging::trivial::trace) << "Trace message";
BOOST_LOG_SEV(lg, logging::trivial::error) << "Error message";
return 0;
}
If this is a clumsy approach and there's a more elegant solution to feed
log messages into SomeLogChannel() (in reality, it's a bit more complex
because it involves a class, a couple interfaces, etc.), don't hesitate
to comment as well. I'm still trying to wrap my mind around the topic.
Thanks a bunch in advance and greets,
Volker
--
@: boost@bartheld.net
Volker