Class: Saxon::XPath::Compiler

Inherits:
Object
  • Object
show all
Extended by:
Forwardable
Defined in:
lib/saxon/xpath/compiler.rb

Overview

An Compiler turns XPath expressions into executable queries you can run against XDM Nodes (like XML documents, or parts of XML documents).

To compile an XPath requires an XPath::Compiler instance. You can create one by calling Compiler.create and passing a Processor, with an optional block for context like bound namespaces and declared variables. Alternately, and much more easily, you can call Processor#xpath_compiler on the Processor instance you’re already working with.

processor = Saxon::Processor.create
compiler = processor.xpath_compiler {
  namespace a: 'http://example.org/a'
  variable 'a:var', 'xs:string'
}
# Or...
compiler = Saxon::XPath::Compiler.create(processor) {
  namespace a: 'http://example.org/a'
  variable 'a:var', 'xs:string'
}
xpath = compiler.compile('//a:element[@attr = $a:var]')
matches = xpath.evaluate(document_node, {
  'a:var' => 'the value'
}) #=> Saxon::XDM::Value

In order to use prefixed QNames in your XPaths, like /ns:name/, then you need to declare prefix/namespace URI bindings when you create a compiler.

It’s also possible to make use of variables in your XPaths by declaring them at the compiler creation stage, and then passing in values for them as XPath run time.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(s9_processor, static_context) ⇒ Compiler

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of Compiler.

Parameters:

  • s9_processor (net.sf.saxon.s9api.Processor) —

    the Saxon Processor to wrap

  • static_context (Saxon::XPath::StaticContext) —

    the static context XPaths compiled using this compiler will have



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# File 'lib/saxon/xpath/compiler.rb', line 60

def initialize(s9_processor, static_context)
  @s9_processor, @static_context = s9_processor, static_context
end

Instance Attribute Details

#declared_namespaces ⇒ Hash<String => String> (readonly)

Returns declared namespaces as prefix => URI hash.

Returns:

  • (Hash<String => String>) —

    declared namespaces as prefix => URI hash




# File 'lib/saxon/xpath/compiler.rb', line 65

#declared_variables ⇒ Hash<Saxon::QName => Saxon::XPath::VariableDeclaration> (readonly)

Returns declared variables as QName => Declaration hash.

Returns:




# File 'lib/saxon/xpath/compiler.rb', line 65

#default_collation ⇒ String (readonly)

Returns the URI of the default declared collation.

Returns:

  • (String) —

    the URI of the default declared collation




# File 'lib/saxon/xpath/compiler.rb', line 65

Class Method Details

.create(processor) { ... } ⇒ Saxon::XPath::Compiler

Create a new XPath::Compiler using the supplied Processor. Passing a block gives access to a DSL for setting up the compiler’s static context.

Parameters:

Yields:

  • An XPath::StaticContext::DSL block

Returns:



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# File 'lib/saxon/xpath/compiler.rb', line 45

def self.create(processor, &block)
  static_context = XPath::StaticContext.define(block)
  new(processor.to_java, static_context)
end

Instance Method Details

#compile(expression) ⇒ Saxon::XPath::Executable

Returns the executable query.

Parameters:

  • expression (String) —

    the XPath expression to compile

Returns:



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# File 'lib/saxon/xpath/compiler.rb', line 74

def compile(expression)
  Saxon::XPath::Executable.new(new_compiler.compile(expression), static_context)
end

#create { ... } ⇒ Saxon::XPath::Compiler

Allows the creation of a new Saxon::XPath::Compiler starting from a copy of this Compiler’s static context. As with create, passing a block gives access to a DSL for setting up the compiler’s static context.

Yields:

  • An XPath::StaticContext::DSL block

Returns:



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# File 'lib/saxon/xpath/compiler.rb', line 84

def create(&block)
  new_static_context = static_context.define(block)
  self.class.new(@s9_processor, new_static_context)
end