Project: Expense Tracker in Dart

Project Goal

Build a personal expense tracker that categorizes spending, tracks balances, and generates monthly summaries. Covers enums, sorting, groupBy, date handling, and formatting.

Full Code

import 'dart:io';

enum Category { food, transport, utilities, entertainment, health, other }

class Expense {
  final int id;
  final String description;
  final double amount;
  final Category category;
  final DateTime date;

  Expense({required this.id, required this.description, required this.amount,
           required this.category, DateTime? date})
      : date = date ?? DateTime.now();

  @override String toString() {
    var d = '$${date.year}-$${date.month.toString().padLeft(2,'0')}-$${date.day.toString().padLeft(2,'0')}';
    return '[$d] $${category.name.toUpperCase().padRight(13)} \$$${amount.toStringAsFixed(2).padLeft(8)} - $description';
  }
}

class ExpenseTracker {
  final List<Expense> _expenses = [];
  int _nextId = 1;

  void add(String desc, double amount, Category cat, {DateTime? date}) {
    _expenses.add(Expense(id: _nextId++, description: desc, amount: amount, category: cat, date: date));
  }

  double get total => _expenses.fold(0, (s, e) => s + e.amount);

  Map<Category, double> get byCategory {
    var result = <Category, double>{};
    for (var e in _expenses) {
      result[e.category] = (result[e.category] ?? 0) + e.amount;
    }
    return result;
  }

  List<Expense> forMonth(int year, int month) =>
      _expenses.where((e) => e.date.year == year && e.date.month == month).toList();

  void monthlyReport(int year, int month) {
    var expenses = forMonth(year, month);
    if (expenses.isEmpty) { print('No expenses for $year-$month'); return; }
    var monthTotal = expenses.fold(0.0, (s, e) => s + e.amount);
    print('\n===== $year-$${month.toString().padLeft(2,'0')} EXPENSE REPORT =====');
    expenses.forEach(print);
    print('\n--- By Category ---');
    var cats = <Category, double>{};
    for (var e in expenses) cats[e.category] = (cats[e.category] ?? 0) + e.amount;
    cats.entries.toList()
      ..sort((a, b) => b.value.compareTo(a.value))
      ..forEach((e) => print('$${e.key.name.padRight(15)} \$$${e.value.toStringAsFixed(2)}'));
    print('\nTotal: \$$${monthTotal.toStringAsFixed(2)}');
  }
}

void main() {
  var tracker = ExpenseTracker();
  var now = DateTime.now();
  var m = now.month;
  var y = now.year;

  tracker.add('Grocery shopping', 45.50, Category.food, date: DateTime(y, m, 1));
  tracker.add('Bus pass', 30.00, Category.transport, date: DateTime(y, m, 2));
  tracker.add('Netflix', 15.99, Category.entertainment, date: DateTime(y, m, 3));
  tracker.add('Electricity bill', 80.00, Category.utilities, date: DateTime(y, m, 4));
  tracker.add('Doctor visit', 120.00, Category.health, date: DateTime(y, m, 5));
  tracker.add('Restaurant lunch', 22.75, Category.food, date: DateTime(y, m, 6));
  tracker.add('Movie tickets', 18.00, Category.entertainment, date: DateTime(y, m, 7));
  tracker.add('Grab ride', 12.50, Category.transport, date: DateTime(y, m, 8));

  tracker.monthlyReport(y, m);
  print('\nAll-time total: \$$${tracker.total.toStringAsFixed(2)}');
}

Challenges

• Add a budget per category and warn when exceeded
• Add recurring expenses (subscriptions)
• Export monthly report to CSV
• Build a Flutter app with pie charts by category