matlab.io.xml.xpath.Evaluator class

Package: matlab.io.xml.xpath

XPath expression evaluator

Description

Use an object of the matlab.io.xml.xpath.Evaluator class to create an XPath expression evaluator.

The matlab.io.xml.xpath.Evaluator class is a handle class.

Class Attributes

ConstructOnLoad	true
HandleCompatible	true

For information on class attributes, see Class Attributes.

Creation

Description

evaluator = matlab.io.xml.xpath.Evaluator() creates an XPath expression evaluator.

Properties

PrefixResolver — Custom prefix resolver

[] (default) | object of subclass of matlab.io.xml.xpath.PrefixResolver

Custom prefix resolver, specified as an object of a subclass of the matlab.io.xml.xpath.PrefixResolver class.

Attributes:

GetAccess	public
SetAccess	public
NonCopyable	true

ResolvePrefixes — Whether to resolve namespace prefixes

true (default) | false

Whether to resolve namespace prefixes, specified as true or false. If the value is true, the evaluator attempts to resolve namespace prefixes that occur in the XPath expression. If you also set the setPrefixResolver property, the evaluator uses the specified resolver to resolve prefixes. If you do not set the setPrefixResolver property, the evaluator uses the parent document to resolve prefixes.

Attributes:

GetAccess	public
SetAccess	public
NonCopyable	true

Methods

Public Methods

compileExpression	compiledExpression = compileExpression(thisEvaluator,source) compiles the specified XPath source expression and returns the result as a matlab.io.xml.xpath.CompiledExpression object. If the expression contains namespace prefixes, you must specify a prefix resolver.
evaluate	Evaluate XPath expression. See evaluate.

Examples

Evaluate an XPath Expression in the Context of an XML File

This example evaluates an XPath expression that finds the nodes with the name Instrument in the file music.xml.

The file music.xml contains this XML markup:

<MusicalEnsemble>
	<Ensemble>
		<Music>Jazz</Music>
            <BandName>Kool Katz</BandName>
		<Instrumentation>
			<Instrument type="wind">Trumpet
            </Instrument>
			<Instrument type="percussion">Piano
                <pianotype>concert grand</pianotype>
            </Instrument>
			<Instrument type="percussion">Drums
                <drumkit>Bass drum</drumkit>
                <drumkit>Floor tom</drumkit>
                <drumkit>Snare drum</drumkit>
                <drumkit>Hi-hat</drumkit>
                <drumkit>Ride cymbal</drumkit>
            </Instrument>
			<Instrument type="string">Bass
                <basstype>upright</basstype>
            </Instrument>
		</Instrumentation>
	</Ensemble>
    <Musicians>
        <Name role="trumpeter">Miles</Name>
        <Name role="vocalist">Roger</Name>
        <Name role="pianist">Diana</Name>
        <Name role="drummer">George</Name>
        <Name role="bassist">John</Name>
    </Musicians>
</MusicalEnsemble>

Define the XPath expression and specify the XML file.

import matlab.io.xml.xpath.*

xpExpr = "//Instrument";
xmlFilePath = "music.xml";

Evaluate the XPath expression and return the nodes as a vector of node objects.

data = evaluate(Evaluator,xpExpr,xmlFilePath,EvalResultType.NodeSet)

data=1×4 object
  1x4 Element array with properties:

    TagName
    HasAttributes
    TextContent
    Children

Algorithms

The MATLAB^® Evaluator object supports the use of the following standard XPath functions in XPath expressions:

• current

• document

• element-available

• format-number

• function-available

• generate-id

• key

• system-property

• unparsed-entity-uri

For more information on definitions and usage of these functions, see XPath and XQuery Functions and Operators 3.1 on the World Wide Web Consortium website.

Version History

Introduced in R2021a