Qt 4.8: QXmlNodeModelIndex Class Reference

Qt Reference Documentation

# QXmlNodeModelIndex Class Reference

The QXmlNodeModelIndex class identifies a node in an XML node model subclassed from QAbstractXmlNodeModel. More...

     #include <QXmlNodeModelIndex>

Note: All functions in this class are reentrant.

This class was introduced in Qt 4.4.

- List of all members, including inherited members

## Public Types

enum | DocumentOrder { Precedes, Follows, Is }
typedef | List
enum | NodeKind { Attribute, Text, Comment, Document, ..., ProcessingInstruction }

## Public Functions

| QXmlNodeModelIndex ()
| QXmlNodeModelIndex ( const QXmlNodeModelIndex & other )
qint64 | additionalData () const
qint64 | data () const
void * | internalPointer () const
bool | isNull () const
const QAbstractXmlNodeModel * | model () const
bool | operator!= ( const QXmlNodeModelIndex & other ) const
bool | operator== ( const QXmlNodeModelIndex & other ) const

## Detailed Description

The QXmlNodeModelIndex class identifies a node in an XML node model subclassed from QAbstractXmlNodeModel.

QXmlNodeModelIndex is an index into an XML node model. It contains:

- A pointer to an XML node model, which is returned by model(), and
- Some data, which is returned by data(), internalPointer(), and additionalData().

Because QXmlNodeModelIndex is intentionally a simple class, it doesn't have member functions for accessing the properties of nodes. For example, it doesn't have functions for getting a node's name or its list of attributes or child nodes. If you find that you need to retrieve this kind of information from your query results, there are two ways to proceed.

- Send the output of your XQuery to an XML receiver, or
- Let your XQuery do all the work to produce the desired result.

The second case is explained by example. Suppose you want to populate a list widget with the values of certain attributes from a set of result elements. You could write an XQuery to return the set of elements, and then you would write the code to iterate over the result elements, get their attributes, and extract the desired string values. But the simpler way is to just augment your XQuery to finding the desired attribute values. Then all you have to do is evaluate the XQuery using the version of QXmlQuery::evaluateTo() that populates a QStringList, which you can send directly to your widget.

QXmlNodeModelIndex doesn't impose any restrictions on the `data` value an QXmlNodeModelIndex should contain. The meaning of the data left to the associated node model. Because QXmlNodeModelIndex depends on a particular subclass of QAbstractXmlNodeModel for its existence, the only way you can create an instance of QXmlNodeModelIndex is by asking the node model to create one for you with QAbstractXmlNodeModel::createIndex(). Since that function is protected, it is usually a good idea to write a public function that creates a QXmlNodeModelIndex from arguments that are appropriate for your particular node model.

A default constructed node index is said to be null, i.e., isNull() returns true.

QXmlNodeModelIndex and QAbstractXmlNodeModel follow the same design pattern used for QModelIndex and QAbstractItemModel.

## Member Type Documentation

### enum QXmlNodeModelIndex::DocumentOrder

Identifies the specific node comparison operator that should be used.

Constant | Value | Description
--- | --- | ---
`QXmlNodeModelIndex::Precedes` | `-1` | Signifies the `\<\<` operator. Test whether the first operand precedes the second in the document.
`QXmlNodeModelIndex::Follows` | `1` | Signifies the `\>\>` operator. Test whether the first operand follows the second in the document.
`QXmlNodeModelIndex::Is` | `0` | Signifies the `is` operator. Test whether two nodes have the same node identity.

### typedef QXmlNodeModelIndex::List

Typedef for QList<QXmlNodeModelIndex>.

### enum QXmlNodeModelIndex::NodeKind

Identifies a kind of node.

Constant | Value | Description
--- | --- | ---
`QXmlNodeModelIndex::Attribute` | `1` | Identifies an attribute node
`QXmlNodeModelIndex::Text` | `64` | Identifies a text node
`QXmlNodeModelIndex::Comment` | `2` | Identifies a comment node
`QXmlNodeModelIndex::Document` | `4` | Identifies a document node
`QXmlNodeModelIndex::Element` | `8` | Identifies an element node
`QXmlNodeModelIndex::Namespace` | `16` | Identifies a namespace node
`QXmlNodeModelIndex::ProcessingInstruction` | `32` | Identifies a processing instruction.

Note that the optional XML declaration at very beginning of the XML document is not a processing instruction

See also QAbstractXmlNodeModel::kind().

## Member Function Documentation

### QXmlNodeModelIndex::QXmlNodeModelIndex ()

Default constructor. Creates an item that is `null`.

See also isNull().

### QXmlNodeModelIndex::QXmlNodeModelIndex ( const QXmlNodeModelIndex & other )

Standard copy constructor. Creates a QXmlNodeModelIndex instance that is a copy of other.

### qint64 QXmlNodeModelIndex::additionalData () const

Returns the second data value. The node index holds two data values. data() returns the first one.

See also data().

### qint64 QXmlNodeModelIndex::data () const

Returns the first data value. The node index holds two data values. additionalData() returns the second one.

See also additionalData().

### void * QXmlNodeModelIndex::internalPointer () const

Returns the first data value as a void* pointer.

See also additionalData().

### bool QXmlNodeModelIndex::isNull () const

Returns true if this QXmlNodeModelIndex is a default constructed value, otherwise false.

A null QXmlNodeModelIndex doesn't represent any node and cannot be used in conjunction with QAbstractXmlNodeModel.

### const QAbstractXmlNodeModel * QXmlNodeModelIndex::model () const

Returns the QAbstractXmlNodeModel that this node index refers to. QXmlNodeModelIndex does not own QAbstractXmlNodeModel and does not keep track of its lifetime, so this pointer will dangle if the QAbstractXmlNodeModel is deallocated first.

There is no setter for the node model because instances of QXmlNodeModelIndex instances are only created with QAbstractXmlNodeModel::createIndex().

### bool QXmlNodeModelIndex::operator!= ( const QXmlNodeModelIndex & other ) const

Returns true if other is the same node as this.

### bool QXmlNodeModelIndex::operator== ( const QXmlNodeModelIndex & other ) const

Returns true if this node is the same as other. This operator does not compare values, children, or names of nodes. It compares node identities, i.e., whether two nodes are from the same document and are found at the exact same place.