Contents

XMLDocument

An XML document as internalized into a logical tree structure.

Declaration

class XMLDocument

Mentioned in

Overview

An XMLDocument object can have multiple child nodes but only one element, the root element. Any other node must be a XMLNode object representing a comment or a processing instruction. If you attempt to add any other kind of child node to an XMLDocument object, such as an attribute, namespace, another document object, or an element other than the root, XMLDocument raises an exception. If you add a valid child node and that object already has a parent, XMLDocument raises an exception. An XMLDocument object may also have document-global attributes, such as XML version, character encoding, referenced DTD, and MIME type.

The initializers of the XMLDocument class read an external source of XML, whether it be a local file or remote website, parse it, and process it into the tree representation. You can also construct an XMLDocument programmatically. There are accessor methods for getting and setting document attributes, methods for transforming documents using XSLT, a method for dynamically validating a document, and methods for printing out the content of an XMLDocument as XML, XHTML, HTML, or plain text.

The XMLDocument class is thread-safe as long as any given instance is used only in one thread.

Subclassing Notes

Methods to Override

To subclass NSXMLDocument you need to override the primary initializer, init(data:options:), and the methods listed below. In most cases, you need only invoke the superclass implementation, adding any subclass-specific code before or after the invocation, as necessary.

By default NSXMLDocument implements the NSObject isEqual(_:) method to perform a deep comparison: two NSXMLDocument objects are not considered equal unless they have the same name, same child nodes, same attributes, and so on. The comparison does not consider the parent node (and hence the node’s location). If you want a different standard of comparison, override isEqual:.

Special Considerations

Because of the architecture and data model of NSXML, when it parses and processes a source of XML it cannot know about your subclass unless you override the class method replacementClass(for:) to return your custom class in place of an NSXML class. If your custom class has no direct NSXML counterpart—for example, it is a subclass of NSXMLNode that represents CDATA sections—then you can walk the tree after it has been created and insert the new node where appropriate.

Topics

Initializing NSXMLDocument Objects

Managing Document Attributes

Setting Document URI

Managing the Root Element

Adding and Removing Child Nodes

Transforming a Document Using XSLT

Writing a Document as XML Data

Validating a Document

Constants

Initializers

See Also

Tree-Based Processing