QXmlName Class Reference
[QtXmlPatterns module]

Detailed Description

The QXmlName class represents the name of an XML node, in an efficient, namespace-aware way.

QXmlName represents the name of an XML node in a way that is both efficient and safe for comparing names. Normally, an XML node represents an XML element or attribute, but QXmlName can also represent the names of other kinds of nodes, e.g., QAbstractXmlReceiver::processingInstruction() and QAbstractXmlReceiver::namespaceBinding().

The name of an XML node has three components: The namespace URI, the local name, and the prefix. To see what these refer to in XML, consider the following snippet.

 <book xmlns:dc='http://purl.org/dc/elements/1.1'
       xmlns='http://example.com/MyDefault'>
     <dc:title>Mobey Dick</dc:title> ...
 </book>

For the element named book, localName() returns book, namespaceUri() returns http://example.com/MyDefault, and prefix() returns an empty string. For the element named title, localName() returns title, namespaceUri() returns http://purl.org/dc/elements/1.1, and prefix() returns dc.

To ensure that operations with QXmlName are efficient, e.g., copying names and comparing them, each instance of QXmlName is associated with a name pool, which must be specified at QXmlName construction time. The three components of the QXmlName, i.e., the namespace URI, the local name, and the prefix, are stored in the name pool mapped to identifiers so they can be shared. For this reason, the only way to create a valid instance of QXmlName is to use the class constructor, where the name pool, local name, namespace URI, and prefix must all be specified.

Note that QXmlName's default constructor constructs a null instance. It is typically used for allocating unused entries in collections of QXmlName.

A side effect of associating each instance of QXmlName with a name pool is that each instance of QXmlName is tied to the QXmlNamePool with which it was created. However, the QXmlName class does not keep track of the name pool, so all the accessor functions, e.g., namespaceUri(), prefix(), localName(), and toClarkName() require that the correct name pool be passed to them. Failure to provide the correct name pool to these accessor functions results in undefined behavior.

Note that a name pool is not an XML namespace. One name pool can represent instances of QXmlName from different XML namespaces, and the instances of QXmlName from one XML namespace can be distributed over multiple name pools.

 <svg xmlns="http://www.w3.org/2000/svg"/>

 <x:svg xmlns:x="http://www.w3.org/2000/svg"/>

 {http://www.w3.org/1999/xhtml/}x:html.

 MyWidget