↑
Main Page

QName class

Namespace

object can then be used in selection statements:

var oWroxNS = new Namespace(“wrox”, “http://www.wrox.com/”);

var oXml = <wrox:root xmlns:wrox=”http://www.wrox.com/”>

<wrox:message>Hello World!</wrox:message>

</wrox:root>;

var sMessage = oXml.oWroxNS::message;

The highlighted line uses the

oWroxNS Namespace

object to select the

<wrox:message>

text

Hello

World!

. If the XML code specifies a namespace, this method must be used when selecting elements in E4X.

The QName class

The

QName

class represents a qualified name for XML elements and attributes. The qualified name is

made up of a namespace prefix and a local name, such as the following:

<wrox:message xmlns:wrox=”http://www.wrox.com/”>Hello World!</wrox:message>

In this code,

wrox:message

is a qualified name, with

wrox

representing a namespace and

message

rep-

resenting the local name (also called tag name). The prefix

wrox

points to a namespace URI of

http://

www.wrox.com/

. A

QName

object can represent the

wrox:message

qualified name like this:

var oWroxNS = new Namespace(“wrox”, “http://www.wrox.com/”);

var oQName = new QName(oWroxNS, “message”);

Using this version of the constructor, a

Namespace

object must be provided to represent the qualified

name. Alternately, a

QName

object can be created without any namespace if one isn’t specified:

var oQName = new QName(“message”);

After the object is created, it has two properties that can be accessed:

uri

and

localName

. The

uri

prop-

erty returns the URI of the namespace specified when the object is created (or an empty string if no

namespace is specified); the

localName

property returns the local-name part of the qualified name. For

example:

var oWroxNS = new Namespace(“wrox”, “http://www.wrox.com/”);

var oQName = new QName(oWroxNS, “message”);

alert(oQName.uri); //outputs “http://www.wrox.com/”

alert(oQName.localName); //outputs “message”

In this example, the

uri

property returns

“http://www.wrox/com/”

and

localName

returns

“mes-

sage”

. These properties are read-only and cause an error if you try to change their values.

The

QName

object overrides the

toString()

object to return a string in the form

uri::localName

, such

“http://www.wrox.com/::message”

in the previous example.

The XML class

As mentioned previously, an

XML

object represents an XML element, meaning that it represents an

ordered list of properties with a name, a parent, a set of attributes, child nodes, and a set of namespaces.

XML

object can be created in one of two ways. The first way is to use its constructor and pass in an

XML string like this:

608

Chapter 20

23_579088 ch20.qxd 3/28/05 11:44 AM Page 608