last-child, etc, pseudo selectors don't work

[paul]

Example in this Gist, http://gist.github.com/639600, I'm trying to select the last DD having a certain class.

The nth-last-child(1) selector works, but last-child does not. Does nokogiri not implement the last-foo selectors?

[flavorjones]

Sure we do:

puts Nokogiri::CSS.xpath_for("dd.foo:last-child")
# => //dd[contains(concat(' ', @class, ' '), ' foo ') and position() = last()]

I think the problem here is a misunderstanding of what last-child means in this context. If you use 'dd:last-child', it means "any element who is named dd and is the last child of its parent.". If you use 'dd.foo:last-child', it means "any element who is named dd and has the class 'foo' and is the last child of its parent. Your gist doesn't contain such an element, and so returns nothing. If you change the html in your gist to be:

<dl>
  <dt>Label</dd>
  <dd class=other>Other Value</dd>

  <dt>Label</dt>
  <dd class=foo>Value</dd>
  <dd class=foo>Trying to select this dd</dd>
  <dd class=foo>Other Value</dd>
</dl>

(note: the last DD now has class 'foo') you'll see that Nokogiri returns the correct element.

In the future, questions like this about CSS are better sent to the mailing list, so that people with similar questions might be able to more easily share in our conversation.

Thanks for using nokogiri!
-mike

[paul]

Changing the class of the last dd to "foo" doesn't help, its not the one that I want to find. I'm trying to find the last dd having class foo. I understand what you're saying about :last-child, meaning "The dd with class foo that is the last child", but then why does :nth-last-child(1) work, when :last-child does not?

[flavorjones]

Ah, OK, then that's a bug in nth-last-child, not a bug in last-child. I'll isolate where the problem is and will update this ticket.

(Reopening)

[flavorjones]

fixing off-by-one with nth-last-child and nth-last-of-type CSS selectors when NOT using an+b notation. closed by bb3cab9.