Time Tracker

Introduction

A commonly required task consists in recording the time a process starts, is paused/resumed, and the time it has ended. The mixin TimeTracker is designed to perform this job. Its methods provide similar functionality to a StopWatch, however instead of elapsed ticks it records a DateTime point whenever its status changes.

The image below shows the available states (grey font) defined by the enum TimeStatus and available transitions (green arrows) defined by the mixin TimeTracker.

Usage

To use this library include time_tracker as a dependency in your pubspec.yaml file.

In addition to methods for recording time points, the mixin TimeTracker provides helper methods for json-serialization. It is recommended that classes with TimeTracker override the getter hashCode and the equality operator such that a deserialized object will compare equal to the original object.

The example below shows how to create the class TennisMatch with the mixin TimeTracker.

mport 'package:exception_templates/exception_templates.dart';
import 'package:time_tracker/time_tracker.dart';

/// Demonstrates how to use TimeTracker.
class TennisMatch with TimeTracker {
  final List<String> players;

  TennisMatch(List<String> players) : players = List.unmodifiable(players);

  /// Constructs an object from a json map.
  factory TennisMatch.fromJson(Map<String, Object?> json) {
    if (json case {'players': List players}) {
      // Use `initTrackerfromJson` to initializer the time tracker.
      return TennisMatch(players.cast<String>())..initTrackerfromJson(json);
    } else {
      throw ErrorOf<TennisMatch>(
        message: 'Error in TennisMatch.fromJson',
        invalidState: ' Found map: $json',
      );
    }
  }

  @override
  Map<String, Object?> toJson() {
    // Providing the entries related to the time tracker.
    final json = trackerToJson();
    // Adding the rest of the entries.
    json['players'] = players;
    return json;
  }

  @override
  int get hashCode => Object.hash(trackerHashCode, players);

  /// Returns `true` if the two instances have the same time status,
  /// time points, and player list.
  @override
  bool operator ==(Object other) {
    return other is TennisMatch &&
        players.equal(other.players) &&
        trackerEqual(other);
  }

  @override
  String toString() {
    return 'TennisMatch: players: $players | status: ${status.name} '
        '| duration: $duration';
  }
}

The program below demonstrates how to use an object of type TennisMatch to start, pause, resume, and end the match. It also shows how to serialize and deserialize the object using 'dart:convert'.

import 'dart:convert';
import '../../test/src/tennis_match.dart';

void main() async {
  print('----- Create an object of type TennisMatch -----');
  final match = TennisMatch(['Tim', 'Andy']);
  print(match);
  match.start();

  print('\nStatus: ${match.status.name} at: ${match.startTime}');

  await Future.delayed(const Duration(seconds: 3), () {
    // Pause object
    match.pause();
    print('Status: ${match.status.name}  at: ${match.lastTimePoint}');
  });

  await Future.delayed(const Duration(seconds: 1), () {
    // Resume object
    match.resume();
    print('Status: ${match.status.name} at: ${match.lastTimePoint}');
  });

  await Future.delayed(const Duration(seconds: 2), () {
    // Mark object as ended.
    match.end();
    print('Status: ${match.status.name}   at: ${match.lastTimePoint}');
  });

  print('');
  print('---------- Getters -------------------');
  print('match.durationAsMicroseconds: ${match.durationAsMicroseconds}\n');
  print('match.durationOfPauses: ${match.durationOfPauses}\n');
  print('match.pauses: ${match.pauses} in us\n');

  print('---------- Json Encoding -------------');
  final jsonString = jsonEncode(match);
  print('Serialized object:');
  print(jsonString);

  var decodedMatch = TennisMatch.fromJson(jsonDecode(jsonString));
  print('');
  print('Deserialized object:');
  print(decodedMatch);

  print('');
  print('match == decodedMatch: ${match == decodedMatch}');
}

$ dart example/bin/time_tracker_example.dart
----- Create an object of type TennisMatch -----
TennisMatch: players: [Tim, Andy] | status: ready | duration: 0:00:00.000000

Status: started at: 2025-10-10 18:17:51.189452
Status: paused  at: 2025-10-10 18:17:54.201310
Status: resumed at: 2025-10-10 18:17:55.212405
Status: ended   at: 2025-10-10 18:17:57.214796

---------- Getters -------------------
match.durationAsMicroseconds: 5014249

match.durationOfPauses: 0:00:01.011095

match.pauses: [1011095] in us

---------- Json Encoding -------------
Serialized object:
{"status":{"timeStatus":"ended"},"timePoints":[1760116671189452,1760116674201310,1760116675212405,1760116677214796],"players":["Tim","Andy"]}

Deserialized object:
TennisMatch: players: [Tim, Andy] | status: ended | duration: 0:00:05.014249

match == decodedMatch: true

Example

The source code of the program shown above can be found in the folder example.

Features and bugs

Please file feature requests and bugs at the issue tracker.