i made a suggestion for this within lighthouse.
Pratik said: "This looks interesting. But I'm not sure if this pattern
belongs to the core or not. You should probably spark a discussion in
the core ML - http://groups.google.com/group/rubyonrails-core"
The Subject can be found here / with a few Pros and Cons...
or - the "code only" version:
self.respond_to?('empty?') && self.empty? ? yield : self