fimber 0.4.0

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fimber #

Extensible logging for Dart and Flutter.

Package is based on famous Android logging library API - Timber, this is library for simplify logging for Flutter. Using similar (as far as Dart lang allows) method API with same concepts for tree and planting logging tree. Also check out flutter_fimber which extends fimber to platform specific output and logging style.

Getting Started #

To start add using it:

Add fimber to pubspec.yaml #

  fimber: ^0.4.0
  • remember about import in file you plan to use Fimber
import 'package:fimber/fimber.dart';

Initialize logging tree on start of your application #

void main() {
  // app code here ...
  // DebugTree options for time elapsed
  // by default DebugTree will output timestamp of the VM/Flutter app
  // to enable elapsed time since planting the tree log

Start using it with static methods: #

import 'fimber.dart';

void main() {
  var parameter = 343.0;
  // use directly
  Fimber.i("Test message $argument");
  Fimber.i("Extra error message", ex: Exception("Test thorwable"));
  // other log levels
  try {
    throw Exception("Exception thrown");
  } catch (e, stacktrace) {
    // providing `stacktrace` will better show where issue was thrown
    // if not provided will use log line location.
    Fimber.i("Error caught.", ex: e, stacktrace: stacktrace);

This will log the value and grab a TAG from stacktrace - that is little costly and if more logs will be done per second.

Colorize logs - ColorizeStyle #

useColors property set to true will use default colors of the logos, you can change the mapping with in colorizeMap for DebugTree and CustomFormatTree The useColors by default is disabled.

ColorizeStyle Aggregates list of AnsiStyle so you can combine styles together.

AnsiStyle is combination of AnsiColor and AnsiSelection values

Here is output of test output.

Colorize Test Output

Create tagged version of Fimber #

And use its instance inside class, you can create logger for a dart file or for a class.

var logger = FimberLog("MY_TAG");

void main() {
  logger.d("Test message");

// or inside a class
class SomeBloc {
  var logger = FimberLog("SomeBloc");
  String fetchMessage() {
    logger.d("About to fetch some data.");
    var data = "load something";

    logger.d("Retrived data (len = ${data.length}");
    return data;

Use block function and pass method that uses logger. #

Use this function to log multiple messages with same tag, allows optional return value. Due to nature of auto-tag generation from stacktrace this block only does it once and create local FimberLog instance to pass into the anonymous method.

    var someMessage = "Test message from inside of block";
    var output = Fimber.block((log) {
      log.d("Started block");
      var i = 0;
      for (i = 0; i < 10; i++) {
        log.d("$someMessage, value: $i");
      log.i("End of block");
      return i;

Deprecated moved to fimber_io package #

Custom line formatters #

Use custom line formatters to define your logging format.

import 'package:fimber_io/fimber_io.dart';


        logFormat: "${CustomFormatTree.TIME_ELAPSED_TOKEN} ${CustomFormatTree
            .MESSAGE_TOKEN} ${CustomFormatTree.TIME_STAMP_TOKEN}"

Use file log tree - the logs will go to a log file (Useful in DartVM apps). There are log rolling with size and time/date interval, so it is possible to setup log output per hour/day or any other time.

see: SizeRollingFileTree or TimedRollingFileTree or use abstract class RollingFileTree to create your own version of rolling log file.

TODO - road map #

Licence #

   Copyright 2018 Mateusz Perlak

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   See the License for the specific language governing permissions and
   limitations under the License.

[0.4.0] - Release of Fimber ready for Web (JS/FlutterWeb) #

  • Moving File loggers to separate fimber_io package
  • Clean up

[0.4.0-dev] - Removing dependency on dart::io. #

  • If want to use File loggers use fimber_io package

[0.3.3] - Deprecating dart:io dependency #

  • Removing FileLogging and moving it to separate package: fimber_io
  • 0.4.0 version will remove dependency on dart::io - so that Fimber can be used in Web projects.

[0.3.2] - Bug fix for Time rolling tree. #

  • #52 issue Fix for check of new file format based on timeSpan intervals.

[0.3.1] - Bug fixes around File rolling tree #

  • initialize outputFileName variable by @sceee
  • removed unnecessary async that caused SizeRollingFileTree constructor to not construct the first logfile correctly before writes to the uninitialized filename could happen by @sceee

[0.3.0] - Code styles updates and bug fixes #

  • Code styles updates based on pedantic lint rules.
  • bug fix for TAG generation taking from correct stacktrace location = index 4.

[0.2.1] - Auto create directory for log files #

[0.2.0] - Colorize logs #

  • Added ANSI colorized option for DebugTree and CustomFormatTree (by default it is disabled)
  • AnsiStyle classes as extra for adding any colorful output for console.

[0.1.11] - FileLog bugfix #

  • FileLog bug fix for conflicts on file append.
  • FileLog uses flush buffer as temporary storage and writes to disk in 2 cases: 1 every 500ms and when ever buffer size exceeds 1kB.
  • Added unit tests for new bug.
  • docs update

[0.1.10] - FileLog append fix, mute levels #

  • bug fix for file log bug where new lines were overriding file not append lines.
  • Added log level muting from Fimber.mute and Fimber.unmute

[0.1.9] - CustomFormatTree and FileLogTree #

  • Custom format tree and File logging tree based on custom format. This will allow DartVM apps to output to defined file.

[0.1.8] - Support for stacktrace optional parameter #

  • Stacktrace optional parameter after adding ex can be provided from try catch block's second parameter
try {
} catch (ex, stacktrace) {
  Fimber.e("log message", ex:ex, stacktrace: stacktrace);  

[0.1.7] - Changed the ex class #

  • Accepting dynamic (any class) on ex property of Logger. This allows to pass Error or Exception or any other value to log statement - toString() is used for printout

[0.1.6] - DebugTree time options #

  • Added Elapsed time option for debug tree logging (useful for server side/dart vm logging)
  • Added Time option for debug tree

[0.1.5] - bug fixes #

  • Bug fix for log tag auto creation inside constructor.
  • Added tests for factory method logging after constructor log tag fix.

[0.1.4] - iOS exception stacktrace logging #

  • no update on fimber, only mirror update for flutter_fimber iOS plugin

[0.1.3] - iOS plugin part for logging #

  • Added support for iOS log output.
  • Un-plant tree option.
  • Block function operation.

[0.1.2] - only dart package form fimber #

  • Small changes around packaging and removing any flutter references.
  • Revert to print from debugPrint for dart only support.
  • DebugTree got printLog method to override to support other solution to print formatted log line tou output stream, will be helpful in AndroidDebugTree (for example).
  • Updates to stacktrace dumping for DebugTree and added method to extract stacktrace.

[0.1.1] - Small updates #

Small updates

[0.1.0] - First Version #

Initial version with Fimber debugging and DebugTree


import 'package:fimber/fimber.dart';

void main() {
  // plant a tree - DebugTree()

  Fimber.d("Test message", ex: Exception("test error"));
  var parameter = 100.0;
  Fimber.w("Test message with parameter: $parameter");

  var logger = FimberLog("MY_TAG");
  logger.d("Test message", ex: Exception("test error"));
  logger.w("Test message with parameter: $parameter");

  try {
    throw Exception("Exception thrown");
    // ignore: avoid_catches_without_on_clauses
  } catch (e, stacktrace) {
    // providing stacktrace will better show where issue was thrown
    Fimber.i("Error caught.", ex: e, stacktrace: stacktrace);
  // save time without auto tag generation on each call in call block.
  Fimber.withTag("TEST BLOCK", (log) {
    log.d("Started block");
    for (var i = 0; i >= 1; i++) {
      log.d("value: $i");
    log.i("End of block");

Use this package as a library

1. Depend on it

Add this to your package's pubspec.yaml file:

  fimber: ^0.4.0

2. Install it

You can install packages from the command line:

with pub:

$ pub get

with Flutter:

$ flutter pub get

Alternatively, your editor might support pub get or flutter pub get. Check the docs for your editor to learn more.

3. Import it

Now in your Dart code, you can use:

import 'package:fimber/fimber.dart';
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Learn more about scoring.

We analyzed this package on Mar 30, 2020, and provided a score, details, and suggestions below. Analysis was completed with status completed using:

  • Dart: 2.7.1
  • pana: 0.13.6

Health suggestions

Format lib/colorize.dart.

Run dartfmt to format lib/colorize.dart.

Format lib/filename_format.dart.

Run dartfmt to format lib/filename_format.dart.

Format lib/fimber_base.dart.

Run dartfmt to format lib/fimber_base.dart.


Package Constraint Resolved Available
Direct dependencies
Dart SDK >=2.0.0-dev.68.0 <3.0.0
Dev dependencies
pedantic ^1.7.0
test ^1.5.1