LogMessage Class Reference

#include <Pt/System/Logger.h>

Logs records with a logger. More...

Inherits NonCopyable.

Public Member Functions
	LogMessage (Logger &logger, const LogLevel &level, bool always=false)
	Constructs a log message for a logger.
	~LogMessage ()
	Destructor.
const LogRecord &	record () const
	Returns the underlying log record.
void	log ()
	Sends the message's log record to the logger.
bool	enabled () const
	Returns true if the record's log level is enabled for the target.
	operator bool () const
	Returns true if the record's log level is enabled for the target.
bool	operator! () const
	Returns true if the record's log level is disabled for the target.
template<typename T>
LogMessage &	operator<< (const T &value)
	Appends value to the log record.
LogMessage &	operator<< (std::ostream &(*op)(std::ostream &))
	Applies op to the log record.
LogMessage &	operator<< (std::ios &(*op)(std::ios &))
	Applies op to the log record.
LogMessage &	operator<< (std::ios_base &(*op)(std::ios_base &))
	Applies op to the log record.
LogMessage &	operator<< (LogMessage &(*pf)(LogMessage &))
	Applies a manipulator to the log message.

Related Symbols
(Note that these are not member symbols.)
LogMessage &	endlog (LogMessage &msg)
	Manipulator to end and send a log-message.

Detailed Description

Log messages can be used to log records with a specific logger. They maintain a log record and a reference to a logger. The log record text can be formatted with the stream output operator, just like for the log records itself:

Pt::System::Logger logger("app.module");
 
Pt::System::LogMessage msg(logger, Pt::System::Info);
if(msg)
{
  msg << "Pi is exactly " << 3
      << " No, I was kidding, its really " << 3.1415
      << Pt::System::endlog;
}

To avoid the costs for formatting, it can be checked if the log level is enabled for the target. A log message can be send mutliple times, so formatting has to be done only once and the logging performance can be increased.

Although it generates more code, it can still make sense to work with log message and log record objects directly. These can improve performance, if the same record has to be logged multiple times, because formatting has to be done only once:

Pt::System::Logger logger("app.module");
Pt::System::LogMessage msg(logger, Pt::System::Info);
msg << "pi is: " << 3.1415;
 
// log for the first time...
msg.log();
 
// ... and later the second time
msg.log();

Constructor & Destructor Documentation

LogMessage()

LogMessage	(	Logger &	logger,
		const LogLevel &	level,
		bool	always = false )

Contructs a log message, which uses logger to log records of the severity level specified by level. If always is true, the message is send to the target without checking the log level. It is assumed that the caller has already checked the log level of the underlying logger and set this flag accordingly. This flag only persists until the message has been sent.