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 class TimeTracker and available transitions (orange arrows) from one state to another.

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 class TimeTracker provides methods for json-serialization. It overrides the equality operator such that objects with the same status and the same recorded time points are considered equal. As such, 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 which extends TimeTracker. With this configuration the object records its own time points. Note: An alternative to extension would be composition. In that case, an instance of TimeTracker could be stored as a class variable.

import 'dart:convert';

import 'package:time_tracker/time_tracker.dart';

/// Demonstrates how to extend TimeTracker.
class TennisMatch extends TimeTracker implements Serializable {
  final players = <String>[];

  /// Note the use of the constructor `super.startNow()`.
  /// This creates an instance of TennisMatch with status: started
  /// and records the instantiation time as the first time point.
  TennisMatch(List<String> players) : super.startNow() {
    this.players.addAll(players);
  }

  /// Constructs an object from a json map.
  TennisMatch.fromJson(Map<String, dynamic> json) : super.fromJson(json) {
    players.addAll(json['players'].cast<String>());
  }

  /// Converts an object to a json map.
  @override
  Map<String, dynamic> toJson() {
    final json = super.toJson();
    json['players'] = List<String>.of(players);
    return json;
  }

  @override
  int get hashCode => Object.hash(super.hashCode, 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 &&
        other.players.equal(players) &&
        other.timePoints.equal(timePoints) &&
        other.status == status;
  }

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

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

  print('----- Create object of type Match -----');
  print('Status: ${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(match);

  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 object of type TennisMatch -----
Status: started at: 2023-02-21 13:13:18.356681
Status: paused at: 2023-02-21 13:13:21.369724
Status: resumed at: 2023-02-21 13:13:22.374468
Status: ended at: 2023-02-21 13:13:24.377429
Match: players: [Tim, Andy] | status: ended | duration: 0:00:05.016004

---------- Json Encoding -------------
Serialized object:
{"status":{"timeStatus":4},"timePoints":[1676985198356681,1676985201369724,1676985202374468,1676985204377429],"players":["Tim","Andy"]}

Deserialized object:
TennisMatch: players: [Tim, Andy] | status: ended | duration: 0:00:05.016004

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.