Time Tracker

Introduction

A commonly required task consists in recording the time a process starts, is paused/resumed, and the time it is completed. An object of type TimeTracker is designed to perform this job. It is similar to a StopWatch, however instead of elapsed ticks it records a DateTime point whenever its status changes.

The image below shows the available states (blue font) defined by the enum TimeStatus and available transitions (orange arrows) defined by the class TimeTracker.

Status changing methods are printed with green font. Calling a status changing method where there is no transition defined has no effect. For example: calling the method end() when the object has status TimeStatus.ready has no effect.

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 equality operator such that a deserialized object will compare equal to the original object.

Usage

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

The example below shows how to construct an object of type TennisMatch with the mixin TimeTracker. The object records its own time points. Note: The getter hashCode and the equality operator are overriden so that decoded objects are equal to the original object.

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

/// Demonstrates how to use TimeTracker.
class TennisMatch with TimeTracker {
  final _players = <String>[];

  TennisMatch(List<String> players) {
    _players.addAll(players);
  }

  /// Constructs an object from a json map.
  TennisMatch.fromJson(Map<String, dynamic> json) {
    if (json case {'players': List players}) {
      _players.addAll(players.cast<String>());

      // Uses the entries of json to initialize the time tracker state.
      initTrackerfromJson(json);
    } else {
      throw ErrorOf<TennisMatch>(
        message: 'Error validating list of players.',
        invalidState: ' Found map: $json',
      );
    }
  }

  @override
  Map<String, dynamic> toJson() {

    // Adds the map entries related to the time tracker.
    final json = trackerToJson();
    json['players'] = List<String>.of(_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'.

void main() async {
  /// Create object (start time is recorded)
  final match = TennisMatch(['Tim', 'Andy'])..start();

  print('----- Create an object of type TennisMatch -----');
  print('Status: ${match.status.name} at: ${match.startTime}');

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

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

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

  print('');
  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 -----
Status: started at: 2024-05-23 18:30:06.167586
Status: paused at: 2024-05-23 18:30:06.176602
Status: resumed at: 2024-05-23 18:30:06.180479
Status: ended at: 2024-05-23 18:30:06.183586

---------- Json Encoding -------------
Serialized object:
{"_status":{"timeStatus":"ended"},
 "_timePoints":[
   1716485406167586,
   1716485406176602,
   1716485406180479,
   1716485406183586,
 ],
 "players":["Tim","Andy"],
}

Deserialized object:
TennisMatch: players: [Tim, Andy] | status: ended | duration: 0:00:00.012123

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.