Use method_missing to allow camel-cased methods to be called by equivalent underscored names. Written with macruby in mind. Note that #respond_to? should be updated too.

alias_underscore.rb

# Faster method, the regex / gsub overhead is invoked only the first time, then an alias is used. I'm not sure that this wouldn't introduce side-effects however. What happens when the original camel-cased method is changed / removed, but it's alias remains inplace?

class Object
  alias orig_method_missing method_missing
  def method_missing name, *args, &block
    if name =~ /\A[a-z\d_]+\z/
      camel_name = name.gsub(/_(.)/) { $1.upcase }
      if self.respond_to? camel_name
        # The 'rescue nil' is because macruby seems to do some odd things with classes sometimes (SBElementArray?):
        self.class.send :alias_method, name, camel_name rescue nil
        return self.send camel_name, *args, &block
      end
    end
    orig_method_missing
  end
end

underscore.rb

# Naive - method_missing and its regexing / gsubing is invoked every method call.

class Object
  alias orig_method_missing method_missing
  def method_missing name, *args, &block
    if name =~ /\A[a-z\d_]+\z/
      name = name.gsub(/_(.)/) { $1.upcase }
      self.send name, *args, &block
    end
    orig_method_missing
  end
end