undefined method `children' for nil:NilClass (NoMethodError) - ruby

Question

I'm trying to revive a simple example of parsing a site with the help of nokogiri and hit about an error undefined method `children' for nil:NilClass (NoMethodError)
require 'open-uri'
url = 'http://www.cubecinema.com/programme'
html = open(url)
puts html
require 'nokogiri'
doc = Nokogiri::HTML(html)
showings = doc.css('.showing').map do |showing|
showing_id = showing['id'].split('_').last.to_i
tags = showing.css('.tags a')
.map{|tag| tag.text.strip}
title_el = showing.at_css('h1 a')
.children
.delete_if{|c| c.name == 'span'}
title = title_el.text.strip
dates = showing.at_css('.start_and_pricing')
.inner_html
.strip
.split('<br>')
.map(&:strip)
.map{|d| DateTime.parse(d)}
description = showing.at_css('.copy')
.text
.delete('[more...]')
.strip
{id: showing_id,
title: title,
tags: tags,
dates: dates,
description: description}
end
I found a possible solution https://translate.googleusercontent.com/translate_c?anno=2&depth=1&rurl=translate.google.com&sl=auto&sp=nmt4&tl=ru&u=https://github.com/dwightjack/grunt-email-boilerplate/issues/12&xid=25657,15700023,15700186,15700191,15700248,15700253&usg=ALkJrhgLkK2xqf-6SfL3K16DBRdtdNH0Cw but it’s not clear what the premailer subtasks are, reading the site didn’t really help them, where do I need to write down these subtasks. I will be very grateful to the clarification either by my mistake or by the way how these subtasks need to be determined, I myself don’t understand and lack experience it is possible.

Answer 1

I am not able to leave just a comment due to lack of reputation, so I can only give advise in answers section.
So, I think that you should check showing.at_css('h1 a') instance first to be sure that it have a children method. Some Nokogiri objects do not have any children (For example meta tag). Hope it helps.

Answer 2

I ran your program locally, and I can't find any tags within the section of code you are scraping.
The reason you are getting this error is because Nokogiri is returning a nil element and you are attempting to delete something which already has no value therefore giving you the NilClass Error.
This is the section of code you are attempting to retrieve "h1 a" from.
<div class="showing" id="event_10427"> <div class="event_image"> <a href="/programme/event/vula-viel-do-not-be-afraid-album-tour,10427/">
<img src="/media/diary/thumbnails/MSJ_vvlive.jpg.600x0_q45.jpg" alt="Picture for event Vula Viel - “Do Not Be Afraid” Album Tour"></a> <span class="tags"> music </span> </div> <!-- div event_image --> <a href="/programme/event/vula-viel-do-not-be-afraid-album-tour,10427/">
<p><span class="pre_title"> Ear Trumpet Music presents </span></p> <h3>Vula Viel - “Do Not Be Afraid” Album Tour</h3> <span class="post_title"> </span> </a> <p></p>
<div class="event_details"> <p class="start_and_pricing"> Thu 28 March // 20:00 <br> </p> <p class="copy">The trio of music makers called Vula Viel weave sparse polyrhythms and intricate rhythm structures around ... [<a class="more" href="/programme/event/vula-viel-do-not-be-afraid-album-tour,10427/">more</a>]</p> </div> </div>
As you can see there is no h1 tags, therefore Nokogiri is returning nil on your search.
You can either change the tag if it's an error on your behalf; or if not every page has a 'h1 a' tag. You will need to check if
title_el = showing.at_css('h3 a')
returns nil before you try to delete it.