Inspired by http://dartgamedevs.org/blog/2012/11/02/Free-Lists-For-Predictable-Game-Performance/ this class stores objects that are no longer used in the game for later reuse.

class ObjectPool {

 static Map<Type, Bag<Poolable>> _objectPools = new Map<Type, Bag<Poolable>>();

 /**
  * Returns a pooled object of [Type] [type]. If there is no object in the pool
  * it will create a new one using [createPoolable].
  */
 static Poolable get(Type type, CreatePoolable createPoolable) {
   Bag<Poolable> pool = _getPool(type);
   var obj = pool.removeLast();
   if (null == obj) {
     obj = createPoolable();
   }
   return obj;
 }

 static Bag<Poolable> _getPool(Type type) {
   var pooledObjects = _objectPools[type];
   if (null == pooledObjects) {
     pooledObjects = new Bag();
     _objectPools[type] = pooledObjects;
   }
   return pooledObjects;
 }

 /**
  * Adds a [poolable] to the [ObjectPool].
  */
 static void add(Poolable poolable) {
   _objectPools[poolable.runtimeType].add(poolable);
 }

 /**
  * Add a specific [amount] of [Poolable]s for later reuse.
  */
 static void addMany(Type type, CreatePoolable createPoolable, int amount) {
   Bag<Poolable> pool = _getPool(type);
   for (int i = 0; i < amount; i++) {
     pool.add(createPoolable());
   }
 }
}