class Object
  def blank?
    respond_to?(:empty?) ? empty? : !self
  end
end

class Hash
  def to_query_string
    self.map { |k, v| "#{k}=#{v}" }.join("&")
  end
end

class String
  def blank?
    self !~ /\S/
  end

  def invalid?
    self !~ /^\d{5}-\d{3}$/
  end

  def clean
    self.gsub "-", ""
  end
end