1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** 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.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example mediaplayer-qml-cppdatamodel
\title Qt SCXML Media Player QML Example (C++ Data Model)
\ingroup examples-qtscxml
\image mediaplayer.png
\brief Sends data to and receives it from a C++ data model.
\e {Media Player QML Example (C++ Data Model)} demonstrates how to access
data from a C++ data model. The data model enables writing C++ code for
\e expr attributes and \c <script> elements. The \e {data part} of the data
model is backed by a subclass of QScxmlCppDataModel, for which the Qt SCXML
compiler (\c qscxmlc) generates the dispatch methods.
The UI is created using Qt Quick.
\include examples-run.qdocinc
\section1 Using the C++ Data Model
We specify the data model as a value of the \e datamodel attribute of the
\c <scxml> element in the SCXML file:
\quotefromfile mediaplayer-qml-cppdatamodel/mediaplayer-cppdatamodel.scxml
\skipto scxml
\printuntil datamodel
The format of the \e datamodel attribute is:
\c {cplusplus:<class-name>:<classdef-header>}. Therefore, we need a file
called \e thedatamodel.h that contains a subclass of QScxmlCppDataModel:
\quotefromfile mediaplayer-qml-cppdatamodel/thedatamodel.h
\skipto qscxmlcppdatamodel.h
\printuntil Q_SCXML_DATAMODEL
QScxmlCppDataModel derives from QObject, so we add the \c Q_OBJECT macro in
the private section of the definition, right after the opening bracket. We
then place the \c Q_SCXML_DATAMODEL macro after \c Q_OBJECT. The macro
expands to the declaration of virtual methods, the implementation of which
is generated by the Qt SCXML compiler.
In the SCXML file, we specify C++ statements in the \c <script> element and
use the \e expr attribute to access the data model:
\quotefromfile mediaplayer-qml-cppdatamodel/mediaplayer-cppdatamodel.scxml
\skipto state
\printuntil </state>
\printuntil </state>
The Qt SCXML compiler generates the various \c evaluateTo methods and
converts the expressions and scripts into lambdas inside those methods in
\e mediaplayer-cppdatamodel.cpp:
\code
bool TheDataModel::evaluateToBool(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
....
return [this]()->bool{ return isValidMedia(); }();
....
}
QVariant TheDataModel::evaluateToVariant(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
....
return [this]()->QVariant{ return media; }();
....
}
void TheDataModel::evaluateToVoid(QScxmlExecutableContent::EvaluatorId id, bool *ok) {
....
[this]()->void{ media = eventData().value(QStringLiteral("media")).toString(); }();
....
}
\endcode
*/
|
