XPath

XPath is a Ruby DSL around a subset of XPath 1.0. Its primary purpose is to facilitate writing complex XPath queries from Ruby code.

Generating expressions

To create quick, one-off expressions, XPath.generate can be used:

XPath.generate { |x| x.descendant(:ul)[x.attr(:id) == 'foo'] }

You can also call expression methods directly on the XPath module:

XPath.descendant(:ul)[XPath.attr(:id) == 'foo']

However for more complex expressions, it is probably more convenient to include the XPath module into your own class or module:

module MyXPaths
  include XPath

  def foo_ul
    descendant(:ul)[attr(:id) == 'foo']
  end

  def password_field(id)
    descendant(:input)[attr(:type) == 'password'][attr(:id) == id]
  end
end

Both ways return an XPath::Expression instance, which can be further modified. To convert the expression to a string, just call #to_s on it. All available expressions are defined in XPath::DSL.

String, Hashes and Symbols

When you send a string as an argument to any XPath function, XPath assumes this to be a string literal. On the other hand if you send in Symbol, XPath assumes this to be an XPath literal. Thus the following two statements are not equivalent:

XPath.descendant(:p)[XPath.attr(:id) == 'foo']
XPath.descendant(:p)[XPath.attr(:id) == :foo]

These are the XPath expressions that these would be translated to:

.//p[@id = 'foo']
.//p[@id = foo]

The second expression would match any p tag whose id attribute matches a 'foo' tag it contains. Most likely this is not what you want.

In fact anything other than a String is treated as a literal. Thus the following works as expected:

XPath.descendant(:p)[1]

Keep in mind that XPath is 1-indexed and not 0-indexed like most other programming languages, including Ruby.

License

See LICENSE.