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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** 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.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\group qml-publishsubscribe
\title QML Publish and Subscribe API Plugin
QML Support for the Qt Publish and Subscribe API.
*/
/*!
\page qml-publishsubscribe.html
\title Publish and Subscribe QML Plugin
\brief A QML plugin for the Qt Publish and Subscribe API.
\section1 Overview
The Publish and Subscribe QML API enables QML applications to access
values stored in the Value Space from QML. The publish/subscribe features
therefore allow an easy means of publishing and receiving events and data.
\note Although the Publish Subscribe plugin simplifies the process of creating
and receiving notifications, various platforms may require special actions
to be taken before the Publisher and Subscribers are created.
\section2 Publisher
The \l ValueSpacePublisher element allows us to publish key-value pairs
of data to a known path. The "known path" is really the "key" of a key/value
pair. The path has the form of a directory structure
path with the keys acting as files at the end of the path. The process
is that the developer declares a \l ValueSpacePublisher element and then
with a given path defines a list of known keys. For example
\qml
ValueSpacePublisher {
id: battery
path: "/power/battery"
keys: ["charge", "charging"]
}
\endqml
To publish a value the key need only be set to the value. Here we see
that the key is expressed as the last name in the path with dot notation
followed by the key name.
\qml
battery.charge = 50
battery.charging = true
\endqml
\section2 Subscriber
The \l ValueSpaceSubscriber element also defines the path to the
key/value. For each \e key a different \l ValueSpaceSubscriber needs to be
declared. In the above example where we used the keys 'charge' and 'charging'
we will need subscribers for each key
\snippet ../../examples/publishsubscribe/battery-charge/battery-subscriber/battery-subscriber.qml 0
Now the values being published can be read and used
\snippet ../../examples/publishsubscribe/battery-charge/battery-subscriber/battery-subscriber.qml 2
\section1 QML Elements
\annotatedlist qml-publishsubscribe
\section1 Examples
\list
\li \l {battery-charge}{Accessing Publish and Subscribe from QML}
\endlist
*/
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