hashery

https://github.com/rubyworks/hashery

The Hashery is a tight collection of Hash-like classes. Included among its many offerings are the auto-sorting Dictionary class, the efficient LRUHash, the flexible OpenHash and the convenient KeyHash. Nearly every class is a subclass of the CRUDHash which defines a CRUD model on top of Ruby's standard Hash making it a snap to subclass and augment to fit any specific use case.