Project: Contact Manager in Dart

Project Goal

Build a contact manager CLI application with full CRUD, search, tagging, JSON export/import, and formatted display. This project combines file I/O, JSON, sorting, and the args package pattern.

Full Code

import 'dart:io';
import 'dart:convert';

class Contact {
  final String id;
  String name;
  String email;
  String phone;
  String? company;
  List<String> tags;

  Contact({required this.id, required this.name, required this.email,
           required this.phone, this.company, List<String>? tags})
      : tags = tags ?? [];

  factory Contact.fromJson(Map<String, dynamic> j) => Contact(
    id: j['id'], name: j['name'], email: j['email'], phone: j['phone'],
    company: j['company'], tags: List<String>.from(j['tags'] ?? []),
  );

  Map<String, dynamic> toJson() => {
    'id': id, 'name': name, 'email': email, 'phone': phone,
    'company': company, 'tags': tags,
  };

  bool matches(String query) {
    var q = query.toLowerCase();
    return name.toLowerCase().contains(q) ||
           email.toLowerCase().contains(q) ||
           phone.contains(q) ||
           (company?.toLowerCase().contains(q) ?? false) ||
           tags.any((t) => t.toLowerCase().contains(q));
  }

  @override String toString() {
    var lines = [
      '  Name:    $name',
      '  Email:   $email',
      '  Phone:   $phone',
    ];
    if (company != null) lines.add('  Company: $company');
    if (tags.isNotEmpty) lines.add('  Tags:    $${tags.join(', ')}');
    return lines.join('\n');
  }
}

class ContactManager {
  final String _dbPath;
  final Map<String, Contact> _contacts = {};
  int _nextId = 1;

  ContactManager([this._dbPath = 'contacts.json']);

  void load() {
    var f = File(_dbPath);
    if (!f.existsSync()) return;
    var data = jsonDecode(f.readAsStringSync()) as Map;
    _nextId = data['nextId'] ?? 1;
    for (var j in (data['contacts'] as List)) {
      var c = Contact.fromJson(j);
      _contacts[c.id] = c;
    }
    print('Loaded $${_contacts.length} contacts');
  }

  void save() {
    File(_dbPath).writeAsStringSync(JsonEncoder.withIndent('  ').convert({
      'nextId': _nextId,
      'contacts': _contacts.values.map((c) => c.toJson()).toList(),
    }));
  }

  Contact add({required String name, required String email, required String phone,
               String? company, List<String>? tags}) {
    var c = Contact(id: 'C$${_nextId++}', name: name, email: email,
                    phone: phone, company: company, tags: tags);
    _contacts[c.id] = c;
    save();
    return c;
  }

  List<Contact> search(String query) =>
      _contacts.values.where((c) => c.matches(query)).toList()
        ..sort((a, b) => a.name.compareTo(b.name));

  List<Contact> get all =>
      _contacts.values.toList()..sort((a, b) => a.name.compareTo(b.name));

  bool delete(String id) {
    if (!_contacts.containsKey(id)) return false;
    _contacts.remove(id);
    save();
    return true;
  }

  void printAll() {
    if (_contacts.isEmpty) { print('No contacts.'); return; }
    print('\n===== Contacts ($${_contacts.length}) =====');
    for (var c in all) {
      print('\n[$${c.id}]');
      print(c);
    }
  }
}

void main(List<String> args) {
  var mgr = ContactManager()..load();

  // Demo usage when no args:
  if (args.isEmpty) {
    // Seed some data if empty
    if (mgr.all.isEmpty) {
      mgr.add(name: 'Alice Johnson', email: 'alice@example.com',
              phone: '+1-555-1234', company: 'Tech Corp', tags: ['friend', 'developer']);
      mgr.add(name: 'Bob Smith', email: 'bob@example.com',
              phone: '+1-555-5678', company: 'Design Studio', tags: ['client']);
      mgr.add(name: 'Carol Lee', email: 'carol@example.com',
              phone: '+855-12-345678', company: 'Startup Inc', tags: ['friend', 'designer']);
      print('Added sample contacts');
    }
    mgr.printAll();

    print('\n--- Search "friend" ---');
    mgr.search('friend').forEach((c) { print('\n$${c.name}'); print(c); });
    return;
  }

  switch (args[0]) {
    case 'add':
      // todo: parse --name, --email, --phone flags
      print('Use: add --name X --email Y --phone Z');
    case 'search':
      if (args.length < 2) { print('Usage: search <query>'); return; }
      var results = mgr.search(args[1]);
      print('Found $${results.length} contacts:');
      results.forEach((c) { print('\n$${c.name}'); print(c); });
    case 'list':
      mgr.printAll();
    case 'delete':
      if (args.length < 2) { print('Usage: delete <id>'); return; }
      print(mgr.delete(args[1]) ? 'Deleted' : 'Not found');
    default:
      print('Commands: add, list, search <q>, delete <id>');
  }
}

Challenges

• Add tag-based filtering (list --tag developer)
• Add contact groups/categories
• Export to vCard (.vcf) format
• Build a Flutter contacts UI with search