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.