XmlRole QML Type
For specifying a role to an XmlListModel. More...
Import Statement: | import QtQuick.XmlListModel 2.14 |
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.
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