Nokogiri Error: undefined method `radiobutton_with' - Why? - ruby

Question

I try to access a form using mechanize (Ruby).
On my form I have a gorup of Radiobuttons.
So I want to check one of them.
I wrote:
target_form = (page/:form).find{ |elem| elem['id'] == 'formid'}
target_form.radiobutton_with(:name => "radiobuttonname")[2].check
In this line I want to check the radiobutton with the value of 2.
But in this line, I get an error:
: undefined method `radiobutton_with' for #<Nokogiri::XML::Element:0x9b86ea> (NoMethodError)

Answer 1

The problem occured because using a Mechanize page as a Nokogiri document (by calling the / method, or search, or xpath, etc.) returns Nokogiri elements, not Mechanize elements with their special methods.
As noted in the comments, you can be sure to get a Mechanize::Form by using the form_with method to find your form instead.
Sometimes, however, you can find the element you want with Nokogiri but not with Mechanize. For example, consider a page with a <select> element that is not inside a <form>. Since there is no form, you can't use the Mechanize field_with method to find the select and get a Mechanize::Form::SelectList instance.
If you have a Nokogiri element and you want the Mechanize equivalent, you can create it by passing the Nokogiri element to the constructor. For example:
sel = Mechanize::Form::SelectList.new( page.at_xpath('//select[#name="city"]') )
In your case where you had a Nokogiri::XML::Element and wanted a Mechanize::Form:
# Find the xml element
target_form = (page/:form).find{ |elem| elem['id'] == 'formid'}
target_form = Mechanize::Form.new( target_form )
P.S. The first line above is more simply achieved by target_form = page.at_css('#formid').