Initializing

By default, the logging package does not do anything useful with the log messages. You must configure the logging level.

Logger.root.level = Level.ALL; // defaults to Level.INFO

First, set the root Level. All messages at or above the current level are sent to the onRecord stream. Available levels are:

• Level.OFF
• Level.DEBUG
• Level.INFO
• Level.WARNING
• Level.ERROR

Then, listen on the onRecord stream for LogRecord events. The LogRecord class has various properties for the message, error, logger name, and more.

Logging messages

Create a Logger with a unique name to easily identify the source of the log messages.

final log = Logger('MyClassName');

Here is an example of logging a debug message and an error:

var future = doSomethingAsync().then((result) {
  log.debug('Got the result: $result');
  processResult(result);
}).catchError((e, stackTrace) => log.severe('Oh noes!', e, stackTrace));

When logging more complex messages, you can pass a closure instead that will be evaluated only if the message is actually logged:

log.debug(() => [1, 2, 3, 4, 5].map((e) => e * 4).join("-"));

Available logging methods are:

• log.debug(logged_content);
• log.info(logged_content);
• log.warning(logged_content);
• log.error(logged_content);