XmlRole QML Type

For specifying a role to an XmlListModel. More...

Import Statement: import QtQuick.XmlListModel 2.13

Properties

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:


  /****************************************************************************
  **
  ** Copyright (C) 2017 The Qt Company Ltd.
  ** Contact: https://www.qt.io/licensing/
  **
  ** This file is part of the documentation of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** Commercial License Usage
  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
  ** Software or, alternatively, in accordance with the terms contained in
  ** a written agreement between you and The Qt Company. For licensing terms
  ** and conditions see https://www.qt.io/terms-conditions. For further
  ** information use the contact form at https://www.qt.io/contact-us.
  **
  ** BSD License Usage
  ** Alternatively, you may use this file under the terms of the BSD license
  ** as follows:
  **
  ** "Redistribution and use in source and binary forms, with or without
  ** modification, are permitted provided that the following conditions are
  ** met:
  **   * Redistributions of source code must retain the above copyright
  **     notice, this list of conditions and the following disclaimer.
  **   * Redistributions in binary form must reproduce the above copyright
  **     notice, this list of conditions and the following disclaimer in
  **     the documentation and/or other materials provided with the
  **     distribution.
  **   * Neither the name of The Qt Company Ltd nor the names of its
  **     contributors may be used to endorse or promote products derived
  **     from this software without specific prior written permission.
  **
  **
  ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/

  import QtQuick 2.0
  import QtQuick.XmlListModel 2.0

  Rectangle {
      width: 300; height: 200

  XmlListModel {
      id: model
      source: "xmlrole.xml"

      // 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)" }
  }

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

  }

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.