# Poco::XML

# class NodeIterator

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

## Description

Iterators are used to step through a set of nodes, e.g. the set of nodes in a NodeList, the document subtree governed by a particular Node, the results of a query, or any other set of nodes. The set of nodes to be iterated is determined by the implementation of the NodeIterator. DOM Level 2 specifies a single NodeIterator implementation for document-order traversal of a document subtree.

A NodeIterator can be directly instantiated using one of its constructors - the DocumentTraversal interface is not needed and therefore not implemented. Unlike most other DOM classes, NodeIterator supports value semantics.

If the NodeIterator's current node is removed from the document, the result of calling any of the movement methods is undefined. This behavior does not conform to the DOM Level 2 Traversal specification.

## Member Summary

Member Functions: accept, currentNodeNP, detach, expandEntityReferences, filter, last, next, nextNode, operator =, previous, previousNode, root, whatToShow

## Constructors

### NodeIterator

NodeIterator(
const NodeIterator & iterator
);

Creates a NodeIterator by copying another NodeIterator.

### NodeIterator

NodeIterator(
Node * root,
unsigned long whatToShow,
NodeFilter * pFilter = nullptr
);

Creates a NodeIterator over the subtree rooted at the specified node.

## Destructor

### ~NodeIterator

~NodeIterator();

Destroys the NodeIterator.

## Member Functions

### currentNodeNP

Node * currentNodeNP() const;

Returns the current node in the set.

Leaves the NodeIterator unchanged.

Warning: This is a proprietary extension to the DOM Level 2 NodeIterator interface.

### detach

void detach();

Detaches the NodeIterator from the set which it iterated over, releasing any computational resources and placing the iterator in the INVALID state. After detach has been invoked, calls to nextNode or previousNode will raise the exception INVALID_STATE_ERR.

### expandEntityReferences

bool expandEntityReferences() const;

The value of this flag determines whether the children of entity reference nodes are visible to the iterator. If false, they and their descendants will be rejected. Note that this rejection takes precedence over whatToShow and the filter. Also note that this is currently the only situation where NodeIterators may reject a complete subtree rather than skipping individual nodes.

To produce a view of the document that has entity references expanded and does not expose the entity reference node itself, use the whatToShow flags to hide the entity reference node and set expandEntityReferences to true when creating the iterator. To produce a view of the document that has entity reference nodes but no entity expansion, use the whatToShow flags to show the entity reference node and set expandEntityReferences to false.

This implementation does not support entity reference expansion and thus always returns false.

### filter

NodeFilter * filter() const;

The NodeFilter used to screen nodes.

### nextNode

Node * nextNode();

Returns the next node in the set and advances the position of the iterator in the set. After a NodeIterator is created, the first call to nextNode() returns the first node in the set.

### operator =

NodeIterator & operator = (
const NodeIterator & iterator
);

Assignment operator.

### previousNode

Node * previousNode();

Returns the previous node in the set and moves the position of the NodeIterator backwards in the set.

### root

Node * root() const;

The root node of the NodeIterator, as specified when it was created.

### whatToShow

unsigned long whatToShow() const;

This attribute determines which node types are presented via the iterator. The available set of constants is defined in the NodeFilter interface. Nodes not accepted by whatToShow will be skipped, but their children may still be considered. Note that this skip takes precedence over the filter, if any.

### accept

bool accept(
Node * pNode
) const;

### last

Node * last();

### next

Node * next() const;

### previous

Node * previous() const;