Event System

Scene includes a built-in type-safe event system for decoupled communication within scenes.

Basic Usage

Listening to Events

class EventScene extends Scene {
  protected initialize(): void {
    // Listen to events
    this.eventSystem.on('player_died', this.onPlayerDied.bind(this));
    this.eventSystem.on('enemy_spawned', this.onEnemySpawned.bind(this));
    this.eventSystem.on('level_complete', this.onLevelComplete.bind(this));
  }

  private onPlayerDied(data: any): void {
    console.log('Player died event');
  }

  private onEnemySpawned(data: any): void {
    console.log('Enemy spawned event');
  }

  private onLevelComplete(data: any): void {
    console.log('Level complete event');
  }
}

Sending Events

public triggerGameEvent(): void {
  // Send event (synchronous)
  this.eventSystem.emitSync('custom_event', {
    message: "This is a custom event",
    timestamp: Date.now()
  });

  // Send event (asynchronous)
  this.eventSystem.emit('async_event', {
    data: "Async event data"
  });
}

API Reference

Method	Description
on(event, callback)	Listen to event
once(event, callback)	Listen once (auto-unsubscribe)
off(event, callback)	Stop listening
emitSync(event, data)	Send event (synchronous)
emit(event, data)	Send event (asynchronous)
clear()	Clear all event listeners

Event Handling Patterns

Centralized Event Management

class EventHandlingScene extends Scene {
  protected initialize(): void {
    this.setupEventListeners();
  }

  private setupEventListeners(): void {
    this.eventSystem.on('game_pause', this.onGamePause.bind(this));
    this.eventSystem.on('game_resume', this.onGameResume.bind(this));
    this.eventSystem.on('player_input', this.onPlayerInput.bind(this));
  }

  private onGamePause(): void {
    // Pause game logic
    this.systems.forEach(system => {
      if (system instanceof GameLogicSystem) {
        system.enabled = false;
      }
    });
  }

  private onGameResume(): void {
    // Resume game logic
    this.systems.forEach(system => {
      if (system instanceof GameLogicSystem) {
        system.enabled = true;
      }
    });
  }

  private onPlayerInput(data: any): void {
    // Handle player input
  }
}

Cleanup Event Listeners

Clean up event listeners on scene unload to avoid memory leaks:

public unload(): void {
  // Clear all event listeners
  this.eventSystem.clear();
}

Use Cases

Category	Example Events
Game State	game_start, game_pause, game_over
Player Actions	player_died, player_jump, player_attack
Enemy Actions	enemy_spawned, enemy_killed
Level Progress	level_start, level_complete
UI Interaction	button_click, menu_open