This is a simple and extensible Logging framework for Dart and Flutter highly inspired by Monolog. It can be used instead of the default print method or log method from the developer package.

Why Monolog?

While developing a larger app for the company I work for I found the need for more granular control over how logging information was being processed. Having more control over how logs are presented and processed can save you a lot of time in situations where going through logs is the only thing you can do to fix a problem.

Having worked with Monolog (PHP) in the past i found that i wanted a similar solution for my situation.

Getting started

There are two parts to this package. First is the creation of a Logger, and the Handlers attached to that Logger. This package contains a simple PrintHandler log handler to get you started.

Add this to the start of your app:

import 'package:monolog/monolog.dart';

final logger = Logger('logger', handlers: [PrintHandler()]);

Later in the app you can use that logger instance to log your messages.

logger.debug('debug');
logger.info('info');
logger.notice('notice');
logger.warning('warning');
logger.error('error');
logger.critical('critical');
logger.alert('alert');
logger.emergency('emergency');

Logger Registry

Using the LoggerRegistry is completely optional. Using the Registry makes it possible for you to get a Logger instance from anywhere in your application.

import 'package:monolog/monolog.dart';

final logger = Logger('logger', handlers: [PrintHandler()]);

LoggerRegistry.instance.put(logger);

By registering the Logger you can easily get it at a later stage in your application. This saves you from putting some global variable in your project.

final logger = LoggerRegistry.instance.get();

The first Logger you add to the LoggerRegistry will be set to the default.

Helpers

Using the LoggerRegistry allows you to also use the helper functions located in the package:monolog/helpers.dart file. The helper functions will use the default logger that is registered in the LoggerRegistry

import 'package:monolog/helpers.dart';

debug('debug');
info('info');
notice('notice');
warning('warning');
error('error');
critical('critical');
alert('alert');
emergency('emergency');

Writing a handler

The examples directory contains a file that shows you how to get started with Monolog. Writing a Handler for a Logger is fairly easy. The only thing you need to do is implement the Handler class methods.

abstract class Handler {
  /// Checks whether the given record will be handled by this handler.
  ///
  bool handles(int level);

  /// Handle a [Record].
  ///
  bool handle(Record record);

  /// Handle a set of records.
  ///
  void handleBatch(List<Record> records);

  /// Disposes any resources attached to the handler.
  ///
  /// When disposing the handler all buffers should be flushed, and any open
  /// resources have to be closed.
  ///
  void dispose() {}
}

In practice:

import 'package:monolog/monolog.dart';

class PrintingHandler implements Handler {
  @override
  bool handle(Record record) {
	print(record.message);

    return true;
  }

  @override
  void handleBatch(List<Record> records) => records.forEach((e) => handle(e));

  @override
  bool handles(int level) => true;

  @override
  void dispose() {}
}

final logger = Logger('logger', handlers: [PrintingHandler()]);

Libraries

helpers
monolog