Non generic version of ComponentMapper from dartemis (remove type cast) High performance component retrieval from entities. Use this wherever you need to retrieve components from entities often and fast.

class ComponentMapper0 {
 ComponentType _type;
 Bag<Component> _components;

 ComponentMapper0(Type componentType, World world) {
   this._type = ComponentTypeManager.getTypeFor(componentType);
   _components = world.componentManager.getComponentsByType(this._type);
 }

 /**
  * Fast but unsafe retrieval of a component for this entity.
  * No bounding checks, so this could throw an ArrayIndexOutOfBoundsExeption,
  * however in most scenarios you already know the entity possesses this component.
  */
 get(Entity e) => _components[e.id];

 /**
  * Fast and safe retrieval of a component for this entity.
  * If the entity does not have this component then null is returned.
  */
 getSafe(Entity e) {
   if(_components.isIndexWithinBounds(e.id)) {
     return _components[e.id];
   }
   return null;
 }

 /**
  * Checks if the entity has this type of component.
  */
 bool has(Entity e) => getSafe(e) != null;
}