Clone this repo:
  1. f4c32e3 Reference docs for message arguments (#77) by Nate Bosch · 2 months ago master
  2. 9561ba0 prepare to release 0.11.4 (#72) by Jacob MacDonald · 4 months ago 0.11.4
  3. c25deb4 Make detached Loggers work regardless of hierarchicalLoggingEnabled (#71) by James D. Lin · 4 months ago
  4. abc1207 Add changelog entry for defaultLevel (#70) by Nate Bosch · 5 months ago
  5. 85f2bc2 Replace _rootLevel with root._level (#69) by James D. Lin · 5 months ago

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Initializing

By default, the logging package does not do anything useful with the log messages. You must configure the logging level and add a handler for the log messages.

Here is a simple logging configuration that logs all messages via print.

Logger.root.level = Level.ALL; // defaults to Level.INFO
Logger.root.onRecord.listen((record) {
  print('${record.level.name}: ${record.time}: ${record.message}');
});

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

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

See the Logger class for the different logging methods.