namespace.rb

class A
  class B
    def self.nyan
      "A::B"
    end
  end
  def self.nyan
    B.nyan
  end
  def self.wan
    ::B.nyan
  end
end


class B
  def self.nyan
    "B"
  end
end

p B.nyan # => "B"
p A.nyan # => "A::B"
p A::B.nyan # => "A::B"
p A.wan # => "B"