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adding more CSS info

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1 parent f7dfcec commit f07b3ca52c3f1930c6a263bea3498c543dc226c7 @tenderlove committed Dec 31, 2009
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  1. +40 −0 nokogiri.markdown
@@ -231,4 +231,44 @@ query could be written in XPath like this:
+Similar to XPath, CSS can use brackets for matching attributes. Let's do a
+couple more XPath to CSS translations. On the left is XPath, on the right is
+ h3[@class] => h3[class]
+ h3[@class = "r"] => h3[class = "r"]
+This syntax works, but CSS provides us with a shorthand for matching the
+"class" attribute. To find all h3 tags whose class attribute contains "r",
+we can say:
+ h3.r
+There is a subtle difference between the two previous examples. The first one
+must be an *exact match* where the second one says "the class attribute must
+contain the value r". That means only the CSS selector will match a tag like
+ <h3 class="r foo">Hi!</h3>
+The XPath selector and our translated CSS selector would not match this tag,
+but the "h3.r" selector would. Most of the time, the CSS class selectors do
+what we want. Only when I need something very specific do I use the bracket
+form in my CSS selectors.
+With this knowledge in hand, we can rewrite our original program using CSS
+ doc = Nokogiri::HTML(open(""))
+ doc.css('h3.r > a.l').each do |node|
+ puts node.text
+ end
+I think the CSS selectors usually result in clear, more concise queries than
+XPath does, so I usually stick to CSS queries in my code. There are some
+tasks which CSS cannot accomplish that XPath can, so it's nice to be able to
+fall back to XPath queries when I need to.
+Next, let's look at some basic node API provided by Nokogiri.
### Basic Node API

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