🚀 Lesson 7: Advanced OOP Features

⏱ 30-45 min 📊 Advanced 🚀 Power Features 🔥 Modern Dart 2026 🔗 Official Source

🚀

Beyond Basic OOP: The Next Level

You've mastered classes and inheritance. Now unlock Dart's secret weapons: enhanced enums, extensions, and mixins!

🎨

Enhanced Enums

Enums with superpowers - properties, methods, and constructors!

🔌

Extensions

Add methods to ANY class - even ones you don't own!

🧬

Mixins

Compose classes from reusable building blocks!

🎯

Today's Project: "Super Logger" System

We'll build a professional logging framework using all advanced OOP features:

📊 Enhanced enum for log levels
🔌 Extensions for string formatting
🧬 Mixins for reusable behaviors
🏭 Factory constructors for flexible creation

Step 1

Enhanced Enums: Enums on Steroids

🔍 Enum Evolution

👴 Old Enums (Pre-2.17)

enum LogLevel {
  debug,
  info,
  warning,
  error
}

// Limited - just named values!

✨ Enhanced Enums (Dart 2.17+)

enum LogLevel {
  debug(0, '🔍'),
  info(1, 'ℹ️'),
  warning(2, '⚠️'),
  error(3, '❌');
  
  final int severity;
  final String icon;
  const LogLevel(this.severity, this.icon);
  
  bool get isError => severity >= 3;
}

🏗️ Interactive Enum Builder

Enum Name:

Values (comma-separated name:code):

Additional Property (name:type):

📄 Generated Enhanced Enum:

enum HttpStatus {
  ok(200, 'OK'),
  notFound(404, 'Not Found'),
  serverError(500, 'Internal Server Error');
  
  final int code;
  final String message;
  
  const HttpStatus(this.code, this.message);
  
  bool get isSuccess => code >= 200 && code < 300;
  bool get isError => code >= 400;
  
  static HttpStatus? fromCode(int code) {
    return values.where((s) => s.code == code).firstOrNull;
  }
}

🧪 Test Your Enum

Step 2

Extensions: Supercharging Existing Classes

🔌 Extension Playground

Add your own methods to built-in types:

📝 String Extensions

🧪 Extension Tester

.capitalize Hello world

.isValidEmail false

.toSlug hello-world

.wordCount 2

📚 Extension Use Cases

🎨 UI Helpers

extension ColorExtension on Color {
  Color get darker => 
    Color.fromARGB(alpha, 
      (red * 0.8).toInt(),
      (green * 0.8).toInt(),
      (blue * 0.8).toInt());
}

📅 Date Formatting

extension DateFormatting on DateTime {
  String get timeAgo {
    final diff = DateTime.now().difference(this);
    if (diff.inDays > 365) return '${(diff.inDays/365).floor()}y ago';
    if (diff.inDays > 30) return '${(diff.inDays/30).floor()}mo ago';
    if (diff.inDays > 0) return '${diff.inDays}d ago';
    return 'today';
  }
}

🔢 Number Formatting

extension NumberFormatting on num {
  String get toFileSize {
    if (this < 1024) return '$this B';
    if (this < 1048576) return '${(this/1024).toStringAsFixed(1)} KB';
    return '${(this/1048576).toStringAsFixed(1)} MB';
  }
}

Step 3

Mixins: Composable Behaviors

🧬 Mixin Composer

Build classes by combining mixins like LEGO blocks!

Available Mixins:

📝 Logger Adds logging capability

✅ Validator Adds validation methods

💾 Cache Adds caching behavior

🔔 Notifier Adds notification system

Your Class:

class UserService

extends BaseService

Click mixins to add them!

Available Methods:

No mixins selected

🌳 Mixin Hierarchy Visualizer

BaseService

UserService

Step 4

Factory Constructors: Flexible Object Creation

🏭 Factory Pattern Simulator

Create User Type:

Select a user type to create!

📄 Factory Constructor Pattern:

class User {
  final String name;
  final String role;
  final List permissions;
  
  User._(this.name, this.role, this.permissions);
  
  factory User.admin(String name) => User._(name, 'Admin', 
    ['read', 'write', 'delete', 'manage_users']);
  
  factory User.regular(String name) => User._(name, 'User', 
    ['read', 'write']);
  
  factory User.guest() => User._('Guest', 'Guest', ['read']);
}

🏆

Build: Super Logger System

📊 Enhanced LogLevel Enum

🔌 String & DateTime Extensions

🧬 Logger Mixins

🎮 Main Application

class SuperLogger with ConsoleLogger, FileLogger, MetricsCollector {
  final String appName;
  final LogLevel minimumLevel;
  
  SuperLogger(this.appName, {this.minimumLevel = LogLevel.debug});
  
  void log(LogLevel level, String message) {
    if (!level.shouldLog(minimumLevel)) return;
    
    logToConsole(level, message);
    collectMetric(level);
    
    if (level.isError) {
      logToFile(message.timestamp);
    }
  }
  
  void debug(String msg) => log(LogLevel.debug, msg);
  void info(String msg) => log(LogLevel.info, msg);
  void warning(String msg) => log(LogLevel.warning, msg);
  void error(String msg) => log(LogLevel.error, msg);
  void fatal(String msg) => log(LogLevel.fatal, msg);
}

void main() {
  final logger = SuperLogger('MyApp', minimumLevel: LogLevel.info);
  
  logger.info('Application started');
  logger.warning('Configuration file not found');
  logger.error('Failed to connect to database');
  logger.debug('This won\'t show (below minimum level)');
  logger.fatal('Critical system failure!');
  
  logger.printMetrics();
}

📤 Logger Output Preview

Click "Run Logger" to see the output!

🎮 Advanced OOP Challenge: Feature Master Quiz

🏆 Score: 0/6

⚡ Streak: 0

⏱ Time: 0s

🧠 Mastery: 0%