An instance of
NSXMLDocument represents an XML document as internalized into a logical tree structure. An
NSXMLDocument 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
NSXMLDocument object, such as an attribute, namespace, another document object, or an element other than the root,
NSXMLDocument raises an exception. If you add a valid child node and that object already has a parent,
NSXMLDocument raises an exception. An
NSXMLDocument object may also have document-global attributes, such as XML version, character encoding, referenced DTD, and MIME type.
- macOS 10.4+
The initializers of the
NSXMLDocument 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
NSXMLDocument 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
NSXMLDocument as XML, XHTML, HTML, or plain text.
The NSXMLDocument class is thread-safe as long as any given instance is used only in one thread.
Methods to Override
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.
NSXMLDocument implements the
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
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.