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Private QObject API: Difference between revisions
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c:\dev\qt5-dev-d\qtquickcontrols2\src\quicktemplates2\.moc\debug\../../../../../../qt5-dev/qtquickcontrols2/src/quicktemplates2/qquickpopup_p.h(71): note: see declaration of 'QQuickPopupPrivate' | c:\dev\qt5-dev-d\qtquickcontrols2\src\quicktemplates2\.moc\debug\../../../../../../qt5-dev/qtquickcontrols2/src/quicktemplates2/qquickpopup_p.h(71): note: see declaration of 'QQuickPopupPrivate' | ||
.moc\debug\moc_qquickpopup_p.cpp(1069): error C2227: left of '->anchors' must point to class/struct/union/generic type | .moc\debug\moc_qquickpopup_p.cpp(1069): error C2227: left of '->anchors' must point to class/struct/union/generic type | ||
== Q_PRIVATE_SLOT == | |||
Similar to Q_PRIVATE_PROPERTY, Q_PRIVATE_SLOT is used when you have a slot in a private class that you want to be considered part of the API of the corresponding public class. Using QQuickItem as an example again, Q_PRIVATE_SLOT is used to declare this private slot in [http://code.qt.io/cgit/qt/qtdeclarative.git/tree/src/quick/items/qquickitem.h?id=b1243b8c9ea0add1b7548428c8b0fcb8ee3ac71a#n455 qquickitem.h]: | |||
private: | |||
Q_PRIVATE_SLOT(d_func(), void _q_resourceObjectDeleted(QObject *)) | |||
The slot itself is declared in [http://code.qt.io/cgit/qt/qtdeclarative.git/tree/src/quick/items/qquickitem_p.h?id=b1243b8c9ea0add1b7548428c8b0fcb8ee3ac71a#n313 qquickitem_p.h]: | |||
void _q_resourceObjectDeleted(QObject *); | |||
[[Category:Developing Qt]] | [[Category:Developing Qt]] |
Revision as of 14:06, 15 March 2018
There are certain QObject macros and conventions that are for use in private Qt APIs only. This page describes them.
Q_PRIVATE_PROPERTY
Introduced here.
This macro is used when you have a C++ class that is public that exposes a property whose type is not public. For example, QQuickItem is a public C++ class that exposes an anchors property, whose type is the private QQuickAnchors class:
Q_PRIVATE_PROPERTY(QQuickItem::d_func(), QQuickAnchors * anchors READ anchors DESIGNABLE false CONSTANT FINAL)
In this case, the macro expects there to be a getter named anchors() in the type returned by QQuickItem::d_func(), which there is:
QQuickAnchors *anchors() const;
When using this macro, it's necessary to include the generated moc file at the end of the corresponding .cpp file:
QT_END_NAMESPACE // ... #include "moc_qquickitem_p.cpp"
If you don't do this, you may see an error like the following (example taken from another class -- replace popup with item and it's the same error):
[...] moc_qquickpopup_p.cpp .moc\debug\moc_qquickpopup_p.cpp(1069): error C2027: use of undefined type 'QQuickPopupPrivate' c:\dev\qt5-dev-d\qtquickcontrols2\src\quicktemplates2\.moc\debug\../../../../../../qt5-dev/qtquickcontrols2/src/quicktemplates2/qquickpopup_p.h(71): note: see declaration of 'QQuickPopupPrivate' .moc\debug\moc_qquickpopup_p.cpp(1069): error C2227: left of '->anchors' must point to class/struct/union/generic type
Q_PRIVATE_SLOT
Similar to Q_PRIVATE_PROPERTY, Q_PRIVATE_SLOT is used when you have a slot in a private class that you want to be considered part of the API of the corresponding public class. Using QQuickItem as an example again, Q_PRIVATE_SLOT is used to declare this private slot in qquickitem.h:
private: Q_PRIVATE_SLOT(d_func(), void _q_resourceObjectDeleted(QObject *))
The slot itself is declared in qquickitem_p.h:
void _q_resourceObjectDeleted(QObject *);