Shares common state across many objects to save memory.

Separates intrinsic (shared) state from extrinsic (unique) state.

class TreeType {
  final String name;
  final String texture; // heavy shared data

  TreeType(this.name, this.texture);
}

class TreeFactory {
  static final Map<String, TreeType> _cache = {};

  static TreeType get(String name, String texture) {
    return _cache.putIfAbsent(name, () => TreeType(name, texture));
  }
}

class Tree {
  final int x, y; // extrinsic state (unique per tree)
  final TreeType type; // intrinsic state (shared)

  Tree(this.x, this.y, this.type);
}

// Usage: 1000 trees but only a few TreeType objects in memory
final oak = TreeFactory.get('Oak', 'oak_texture.png');
final trees = [for (var i = 0; i < 1000; i++) Tree(i, i * 2, oak)];