Object foo = [[Foo alloc] init]Using this invocation, foo could be any sort of Object, and init could return any sort of Object. Ruby (and most other OO languages, for that matter) combine the alloc-init into a 'new' method:
foo = Foo.newThe problem is that the object returned is a Foo, at least unless a class supplied its own specialized new.
In a short paper I've written, Creating Alternate Ruby Objects, I discuss a generalized mechanism that allows object remapping in new. This enables a class' new method to return a different object than the one allocated, according to decisions made in the initialize method.
The mechanism has been added to the release 1.0.4 of my eymiha rubygem in my Chunks of Ruby Infrastructure Project on RubyForge.