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39
40#include "qqmlparserstatus.h"
41
42QT_BEGIN_NAMESPACE
43
44/*!
45 \class QQmlParserStatus
46 \since 5.0
47 \inmodule QtQml
48 \brief The QQmlParserStatus class provides updates on the QML parser state.
49
50 QQmlParserStatus provides a mechanism for classes instantiated by
51 a QQmlEngine to receive notification at key points in their creation.
52
53 This class is often used for optimization purposes, as it allows you to defer an
54 expensive operation until after all the properties have been set on an
55 object. For example, QML's \l {Text} element uses the parser status
56 to defer text layout until all of its properties have been set (we
57 don't want to layout when the \c text is assigned, and then relayout
58 when the \c font is assigned, and relayout again when the \c width is assigned,
59 and so on).
60
61 Be aware that QQmlParserStatus methods are only called when a class is instantiated
62 by a QQmlEngine. If you create the same class directly from C++, these methods will
63 not be called automatically. To avoid this problem, it is recommended that you start
64 deferring operations from classBegin instead of from the initial creation of your class.
65 This will still prevent multiple revaluations during initial binding assignment in QML,
66 but will not defer operations invoked from C++.
67
68 To use QQmlParserStatus, you must inherit both a QObject-derived class
69 and QQmlParserStatus, and use the Q_INTERFACES() macro.
70
71 \code
72 class MyObject : public QObject, public QQmlParserStatus
73 {
74 Q_OBJECT
75 Q_INTERFACES(QQmlParserStatus)
76
77 public:
78 MyObject(QObject *parent = 0);
79 ...
80 void classBegin();
81 void componentComplete();
82 }
83 \endcode
84*/
85
86/*! \internal */
87QQmlParserStatus::QQmlParserStatus()
88: d(nullptr)
89{
90}
91
92/*! \internal */
93QQmlParserStatus::~QQmlParserStatus()
94{
95 if(d)
96 (*d) = nullptr;
97}
98
99/*!
100 \fn void QQmlParserStatus::classBegin()
101
102 Invoked after class creation, but before any properties have been set.
103*/
104
105/*!
106 \fn void QQmlParserStatus::componentComplete()
107
108 Invoked after the root component that caused this instantiation has
109 completed construction. At this point all static values and binding values
110 have been assigned to the class.
111*/
112
113QT_END_NAMESPACE
114

source code of qtdeclarative/src/qml/qml/qqmlparserstatus.cpp