Code Sample – Game Engine Core

public class Engine
{
  private var systems_          :Vector.<ISystem> = null;
  private var injector_         :Injector         = null;
  private var entitiesToDestroy_:Vector.<Entity>  = null;
  
  public function Engine(stage:Stage)
  {
    systems_           = new Vector.<ISystem>();
    injector_          = new Injector();
    entitiesToDestroy_ = new Vector.<Entity>();
    
    injector_.map(Stage).toValue(stage);
    injector_.map(Engine).toValue(this);
  }
  
  public function getInjector():Injector 
  { return injector_; }
  
  public function update(dt:Number):void
  {
    var i:int, len:int;
    for (i = 0, len = systems_.length; i < len; ++i)
    {
      if (systems_[i].active) systems_[i].update(dt);
    }
    
    //remove entities marked for destruction from engine
    for 
    (
      i = 0, len = entitiesToDestroy_.length; 
      i < len; ++i
    )
    {
      var entity:Entity = entitiesToDestroy_[i];
      
      //destroy components
      entity.dispose();
      
      //unroll dependency
      injector_.unmap(Entity, entity.name());
      entity.setInjector(null);
    }
    entitiesToDestroy_.length = 0;
  }
  
  public function addSystem(SystemClass:Class, ...params):*
  {
    //check duplicate system
    if (injector_.satisfies(SystemClass))
      throw new Error
        ("System " + SystemClass + " already added.");
    
    //add system to engine
    var system:ISystem = construct(SystemClass, params);
    
    //map injector
    injector_.map(SystemClass).toValue(system);
    
    //initialize system
    systems_.push(system);
    system.setInjector(injector_);
    
    injector_.injectInto(system);
    system.init();
    
    return system;
  }
  
  public function removeSystem(SystemClass:Class):void
  {
    //check system existence
    if (!injector_.satisfies(SystemClass)) 
      throw new Error
        ("System " + SystemClass + " not found.");
    
    var system:ISystem = getInstance(SystemClass);
    
    //dispose system
    system.dispose();
    
    //remove system from engine
    systems_.splice(systems_.indexOf(system), 1);
    system.setInjector(null);
    
    //unmap injector
    injector_.unmap(SystemClass);
  }
  
  public function getInstance(SystemClass:Class):*
  {
    return injector_.getInstance(SystemClass);
  }
  
  private var entityCounter_:uint = 0;
  public function createEntity(name:String = null):Entity
  {
    //check duplicate entity name
    if (injector_.satisfies(Entity, name)) 
      throw new Error
        ("Entity named\"" + name + "\" already exists.");
    
    if (!name) name = "__entity" + entityCounter_++;
    
    //add entity to engine
    var entity:Entity = new Entity(name);
    injector_.map(Entity, name).toValue(entity);
    
    //inject child injector
    var childInjector:Injector = 
      injector_.createChildInjector();
    
    childInjector.map(Entity).toValue(entity);
    entity.setInjector(childInjector);
    
    return entity;
  }
  
  public function destroyEntity(name:String):void
  {
    //check entity name existence
    if (!injector_.satisfies(Entity, name)) 
      throw new Error
        ("Entity named\"" + name + "\" does not exist.");
    
    entitiesToDestroy_.push(getEntity(name));
  }
  
  public function getEntity(name:String):Entity
  {
    return injector_.getInstance(Entity, name);
  }
}