o.respond_to?(:empty?) and o.empty? Fails with: "undefined method `empty?`" - ruby-on-rails

Question

so how is that possible?
I have a Module, that puts a Ruby Object at the end of the renderd page in a nice structured HTML. So i recurse through the given object and build the HTML output. The following is an excerpt of the code where the error is thrown.
EDIT:(had a copy error in code)
o=some object
nicer=if o.respond_to?(:empty?) and o.empty?
add_class='empty'
'empty ' + class_name
else
case o
when TrueClass then
"TRUE"
when FalseClass then
"FALSE"
when Array
#some more when's
the error thrown: undefined method 'empty?' for #Journey::Routes:0x123456
the object (o) it self is ActionDispatch::Routing::RouteSet
again: how is that possible?
EDIT: Stack: (there is the bad one ...)
actionpack (3.2.13) lib/action_dispatch/routing/route_set.rb:366:in `empty?'
lib/tech_draw.rb:90:in `format_nice'
lib/tech_draw.rb:101:in `block in format_nice'
lib/tech_draw.rb:100:in `each'
lib/tech_draw.rb:100:in `map'
lib/tech_draw.rb:100:in `format_nice'
lib/tech_draw.rb:124:in `block in format_nice'
lib/tech_draw.rb:123:in `map'
lib/tech_draw.rb:123:in `format_nice'
lib/tech_draw.rb:13:in `block in say'
lib/tech_draw.rb:13:in `map'
lib/tech_draw.rb:13:in `say'
lib/tech_draw.rb:13:in `map'
lib/tech_draw.rb:6:in `say'
app/controllers/home_controller.rb:131:in `any_page'
actionpack (3.2.13) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
...

Answer 1

How is that possible? Easy:
class Thing
def respond_to? *args
true
end
end
o = Thing.new
o.respond_to?(:empty?) and o.empty?
# => NoMethodError: undefined method `empty?' for #<Thing:0x00000100ae2558>
Although why is it happening in this case is another matter.
ActionDispatch::Routing::RouteSet#empty? appears to call empty? on routes object. Assuming this object is an instance of Journey::Routes that would explain the error, as Journey::Routes doesn’t have an empty? method. (In current Rails versions Journey is part of Rails itself, but in Rails 3.2 it is separate).
I don’t why this is happening in your case though.