XmlRole QML Type

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

Import Statement:

import QtQuick.XmlListModel 2.13

• 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:

/****************************************************************************
**
** 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.
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**     notice, this list of conditions and the following disclaimer in
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**     distribution.
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****************************************************************************/

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.