Class

XMLDocument

An XML document as internalized into a logical tree structure.

Declaration

class XMLDocument : XMLNode

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

init(contentsOf: URL, options: XMLNode.Options)

Initializes and returns an NSXMLDocument object created from the XML or HTML contents of a URL-referenced source

init(data: Data, options: XMLNode.Options)

Initializes and returns an NSXMLDocument object created from an NSData object.

init(rootElement: XMLElement?)

Returns an NSXMLDocument object initialized with a single child, the root element.

init(xmlString: String, options: XMLNode.Options)

Initializes and returns an NSXMLDocument object created from a string containing XML markup text.

class func replacementClass(for: AnyClass) -> AnyClass

Overridden by subclasses to substitute a custom class for an NSXML class that the parser uses to create node instances.

Managing Document Attributes

var characterEncoding: String?

Sets the character encoding of the receiver to encoding,

var documentContentKind: XMLDocument.ContentKind

Sets the kind of output content for the receiver.

var dtd: XMLDTD?

Returns an XMLDTD object representing the internal DTD associated with the receiver.

var isStandalone: Bool

Sets a Boolean value that specifies whether the receiver represents a standalone XML document.

var mimeType: String?

Returns the MIME type for the receiver.

var version: String?

Sets the version of the receiver’s XML.

Managing the Root Element

func rootElement() -> XMLElement?

Returns the root element of the receiver.

func setRootElement(XMLElement)

Set the root element of the receiver.

Adding and Removing Child Nodes

func addChild(XMLNode)

Adds a child node after the last of the receiver’s existing children.

func insertChild(XMLNode, at: Int)

Inserts a node object at specified position in the receiver’s array of children.

func insertChildren([XMLNode], at: Int)

Inserts an array of children at a specified position in the receiver’s array of children.

func removeChild(at: Int)

Removes the child node of the receiver located at a specified position in its array of children.

func replaceChild(at: Int, with: XMLNode)

Replaces the child node of the receiver located at a specified position in its array of children with another node.

func setChildren([XMLNode]?)

Sets the child nodes of the receiver.

Transforming a Document Using XSLT

func object(byApplyingXSLT: Data, arguments: [String : String]?) -> Any

Applies the XSLT pattern rules and templates (specified as a data object) to the receiver and returns a document object containing transformed XML or HTML markup.

func object(byApplyingXSLTString: String, arguments: [String : String]?) -> Any

Applies the XSLT pattern rules and templates (specified as a string) to the receiver and returns a document object containing transformed XML or HTML markup.

func objectByApplyingXSLT(at: URL, arguments: [String : String]?) -> Any

Applies the XSLT pattern rules and templates located at a specified URL to the receiver and returns a document object containing transformed XML markup or an NSData object containing plain text, RTF text, and so on.