Qt 5.8 | Qt Quick | QML Types | XmlRole QML Type

Qt 5.8.0 Reference Documentation

# XmlRole QML Type

For specifying a role to an XmlListModel More...

Import Statement: | import QtQuick.XmlListModel 2.0

- List of all members, including inherited members

## Properties

- isKey : bool
- name : string
- query : string

## Detailed Description

See also Qt QML.

## Property Documentation

isKey : bool

Defines whether this is a key role. Key roles are used to determine whether a set of values should be updated or added to the XML list model when XmlListModel::reload() is called.

See also XmlListModel.

name : string

The name for the role. This name is used to access the model data for this role.

For example, the following model has a role named "title", which can be accessed from the view's delegate:

      XmlListModel {
          id: xmlModel
          // ...
          XmlRole {
              name: "title"
              query: "title/string()"
          }
      }

      ListView {
          model: xmlModel
          delegate: Text { text: title }
      }

query : string

The relative XPath expression query for this role. The query must be relative; it cannot start with a '/'.

For example, if there is an XML document like this:

      <?xml version="1.0" encoding="iso-8859-1" ?>
      <catalog>
          <book type="Online" wanted="true">
              <title>Qt 5 Cadaques</title>
              <year>2014</year>
              <author>Juergen Bocklage-Ryannel</author>
              <author>Johan Thelin</author>
          </book>
          <book type="Hardcover">
              <title>C++ GUI Programming with Qt 4</title>
              <year>2006</year>
              <author>Jasmin Blanchette</author>
              <author>Mark Summerfield</author>
          </book>
          <book type="Paperback">
              <title>Programming with Qt</title>
              <year>2002</year>
              <author>Matthias Kalle Dalheimer</author>
          </book>
       </catalog>

Here are some valid XPath expressions for XmlRole queries on this document:

      XmlListModel {
          id: model
          ...
          // XmlRole queries will be made on <book> elements
          query: "/catalog/book"

          // query the book title
          XmlRole { name: "title"; query: "title/string()" }

          // query the book's year
          XmlRole { name: "year"; query: "year/number()" }

          // query the book's type (the '@' indicates 'type' is an attribute, not an element)
          XmlRole { name: "type"; query: "@type/string()" }

          // query the book's first listed author (note in XPath the first index is 1, not 0)
          XmlRole { name: "first_author"; query: "author[1]/string()" }

          // query the wanted attribute as a boolean
          XmlRole { name: "wanted"; query: "boolean(@wanted)" }
      }

Accessing the model data for the above roles from a delegate:

      ListView {
          width: 300; height: 200
          model: model
          delegate: Column {
              Text { text: title + " (" + type + ")"; font.bold: wanted }
              Text { text: first_author }
              Text { text: year }
          }

See the W3C XPath 2.0 specification for more information.