Clone this repo:
  1. 50b32dc Use correct config for pkg/test on bots by Kevin Moore · 9 months ago master
  2. c2c7765 Fixing some doc comments by Sam Rawlins · 1 year, 3 months ago 0.11.3+1
  3. ca7f455 cleanup .gitignore by Kevin Moore · 1 year, 3 months ago
  4. b0b255a dartfmt by Kevin Moore · 1 year, 3 months ago
  5. 49b983d save non-string object on LogRecord (#28) by Jason Aguilon · 1 year, 6 months ago 0.11.3


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;
Logger.root.onRecord.listen((LogRecord rec) {
  print('${}: ${rec.time}: ${rec.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 Logger log = new 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');
}).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.