Hi, If you have been following trunk very recently you probably know. The Hash class now has a new implementation. So far I'm happy with the changes that are in trunk, and here are the details. - The Hash class is still a subclass of NSMutableDictionary. - All the Hash methods are not defined on Hash anymore, but on NSDictionary instead. The methods have been re-implemented to use the CF APIs. It means that you can for example call #has_key? on all dictionaries, created by Ruby (via the Hash class) or by Objective-C (as a NSCFDictionary object). Trying to call a method that will change the dictionary on an immutable dictionary will raise an exception ("can't modify immutable hash"). - To implement the semantics of the previous Hash class (such as the possibility to freeze it, or specify an "if none" value/proc), MacRuby allocates at demand a data structure and uses a feature of the Objective-C GC to associate/attach it to the dictionary. Once the dictionary is collected, the data structure is also collected at the same time (w00t!). So far, with these changes, MacRuby builds (yeepee!) and most of the tests in test/ruby/test_hash.rb are passing. Things that are not working yet: - Tainting objects. We need to attach the taint flag in the attached structure (like we do with the frozen state). - Passing a false value. Qfalse is 0 in Ruby core, and apparently CFDictionary (via CFDictionaryGetValueIfPresent) has some problems to remove it (though lookups are working). This should anyway be addressed once "false" is something different than 0 in the core. - Hash#compare_by_identity. Supporting that wouldn't be hard by calling some private APIs in CFDictionary. We can now start replacing Array. I proposed on ruby-core to deprecate RARRAY_PTR for element access, which we won't be able to efficiently support. Nobu-san proposed RARRAY_AT() which should work for us. Also, Ben and I have been brainstorming on Monday about future changes, and here is what we decided: http://trac.macosforge.org/projects/ruby/wiki/MacRubyBrainstorming Laurent