watircraft page, step definition, and method to call should assertion on a page object using gherkin text

gistfile1.rb

#
# detail_reports_page.rb
#
class DetailReportsPage < ::Taza::Page
  element(:add_report) {browser.link(:href, 'javascript:createReport();')}
  field(:level_dropdown) {browser.select_list(:name, 'Level')}
end 

#
# steps.rb
# example steps:
# Then the detail reports page add report button exists
# Then the detail reports page level dropdown does not exist
# Then the summary page export link does not exist
#
Then /^the (.+? page) (.+?) (does not )?exists?$/ do |page, obj_desc, negation|
  case obj_desc
  when / button$/
    obj_desc.gsub!(/ button$/, '')
    page_obj_should(page, obj_desc, nil, negation, :exist)
  when / link$/
    obj_desc.gsub!(/ link$/, '')
    page_obj_should(page, obj_desc, nil, negation, :exist)
  else
    page_obj_should(page, obj_desc, nil, negation, :exist)
  end
end

#
# method.rb
#
# evaluate page object with should or should_not assertion
# @param [String, #to_s] page - gherkin description of the watircraft page object
# @param [String, #to_s] obj_desc - gherkin description of the object on the page
# @param [String] attribute - attribute or method chain appended to the page object. 
#  - use nil for no attribute
# @param [Boolean] negation - true evaluates page object with should_not instead of should
# @param [String, #to_s] matcher - matcher and, if applicable, its parameters
def page_obj_should(page, obj_desc, attribute, negation, matcher)
  if negation
    should_case = '.should_not '
  else
    should_case = '.should '
  end
  page_object_string = obj_desc.computerize
  
  # when the page object evaluates to a String object,
  # or when an UnknownObjectException is raised,
  # then reference the built-in '_field' object instead.
  begin
    if eval( page.computerize + '.' + page_object_string ).class == String
      page_object_string = page_object_string << '_field'
    end
  rescue Watir::Exception::UnknownObjectException => e
    page_object_string = page_object_string << '_field'
  end

  eval [page.computerize, page_object_string, attribute].compact.join('.') << should_case << matcher.to_s
end