class Attr

File Information

Library: XML
Package: DOM
Header: Poco/DOM/Attr.h


The Attr interface represents an attribute in an Element object. Typically the allowable values for the attribute are defined in a document type definition.

Attr objects inherit the Node interface, but since they are not actually child nodes of the element they describe, the DOM does not consider them part of the document tree. Thus, the Node attributes parentNode, previousSibling, and nextSibling have a null value for Attr objects. The DOM takes the view that attributes are properties of elements rather than having a separate identity from the elements they are associated with; this should make it more efficient to implement such features as default attributes associated with all elements of a given type. Furthermore, Attr nodes may not be immediate children of a DocumentFragment. However, they can be associated with Element nodes contained within a DocumentFragment. In short, users and implementors of the DOM need to be aware that Attr nodes have some things in common with other objects inheriting the Node interface, but they also are quite distinct.

The attribute's effective value is determined as follows: if this attribute has been explicitly assigned any value, that value is the attribute's effective value; otherwise, if there is a declaration for this attribute, and that declaration includes a default value, then that default value is the attribute's effective value; otherwise, the attribute does not exist on this element in the structure model until it has been explicitly added. Note that the nodeValue attribute on the Attr instance can also be used to retrieve the string version of the attribute's value(s).

In XML, where the value of an attribute can contain entity references, the child nodes of the Attr node provide a representation in which entity references are not expanded. These child nodes may be either Text or EntityReference nodes. Because the attribute type may be unknown, there are no tokenized attribute values.


Direct Base Classes: AbstractNode

All Base Classes: AbstractNode, DOMObject, EventTarget, Node

Member Summary

Member Functions: copyNode, getNodeValue, getValue, innerText, localName, name, namespaceURI, nodeName, nodeType, ownerElement, parentNode, prefix, previousSibling, setNodeValue, setValue, specified, value

Inherited Functions: addEventListener, appendChild, attributes, autoRelease, bubbleEvent, captureEvent, childNodes, cloneNode, copyNode, dispatchAttrModified, dispatchCharacterDataModified, dispatchEvent, dispatchNodeInserted, dispatchNodeInsertedIntoDocument, dispatchNodeRemoved, dispatchNodeRemovedFromDocument, dispatchSubtreeModified, duplicate, events, eventsSuspended, firstChild, getNodeByPath, getNodeByPathNS, getNodeValue, hasAttributes, hasChildNodes, innerText, insertAfterNP, insertBefore, isSupported, lastChild, localName, namespaceURI, nextSibling, nodeName, nodeType, nodeValue, normalize, ownerDocument, parentNode, prefix, previousSibling, release, removeChild, removeEventListener, replaceChild, setNodeValue, setOwnerDocument


Attr protected

    Document * pOwnerDocument,
    const Attr & attr

Attr protected

    Document * pOwnerDocument,
    Element * pOwnerElement,
    const XMLString & namespaceURI,
    const XMLString & localName,
    const XMLString & qname,
    const XMLString & value,
    bool specified = true


~Attr protected virtual


Member Functions

getNodeValue virtual

const XMLString & getNodeValue() const;

getValue inline

const XMLString & getValue() const;

Returns the value of the attribute as a string. Character and general entity references are replaced with their values. See also the method getAttribute on the Element interface.

innerText virtual

XMLString innerText() const;

localName virtual

const XMLString & localName() const;

name inline

const XMLString & name() const;

Returns the name of this attribute.

namespaceURI virtual

const XMLString & namespaceURI() const;

nodeName virtual

const XMLString & nodeName() const;

nodeType virtual

unsigned short nodeType() const;

ownerElement inline

Element * ownerElement() const;

The Element node this attribute is attached to or null if this attribute is not in use.

parentNode virtual

Node * parentNode() const;

prefix virtual

XMLString prefix() const;

previousSibling virtual

Node * previousSibling() const;

setNodeValue virtual

void setNodeValue(
    const XMLString & value


void setValue(
    const XMLString & value

Sets the value of the attribute as a string. This creates a Text node with the unparsed contents of the string. I.e. any characters that an XML processor would recognize as markup are instead treated as literal text. See also the method setAttribute on the Element interface.

specified inline

bool specified() const;

If this attribute was explicitly given a value in the original document, this is true; otherwise, it is false. Note that the implementation is in charge of this attribute, not the user. If the user changes the value of the attribute (even if it ends up having the same value as the default value) then the specified flag is automatically flipped to true. To re-specify the attribute as the default value from the DTD, the user must delete the attribute. The implementation will then make a new attribute available with specified set to false and the default value (if one exists). In summary:

  • If the attribute has an assigned value in the document then specified is true, and the value is the assigned value.
  • If the attribute has no assigned value in the document and has a default value in the DTD, then specified is false, and the value is the default value in the DTD.
  • If the attribute has no assigned value in the document and has a value of #IMPLIED in the DTD, then the attribute does not appear in the structure model of the document.
  • If the attribute is not associated to any element (i.e. because it was just created or was obtained from some removal or cloning operation) specified is true.

value inline

const XMLString & value() const;

Returns the value of the attribute as a string. Character and general entity references are replaced with their values. See also the method getAttribute on the Element interface.

copyNode protected virtual

Node * copyNode(
    bool deep,
    Document * pOwnerDocument
) const;