diff options
Diffstat (limited to 'src/corelib/doc/src/objectmodel/properties.qdoc')
| -rw-r--r-- | src/corelib/doc/src/objectmodel/properties.qdoc | 35 |
1 files changed, 26 insertions, 9 deletions
diff --git a/src/corelib/doc/src/objectmodel/properties.qdoc b/src/corelib/doc/src/objectmodel/properties.qdoc index 39f5e80eaa..d1690c5908 100644 --- a/src/corelib/doc/src/objectmodel/properties.qdoc +++ b/src/corelib/doc/src/objectmodel/properties.qdoc @@ -53,16 +53,22 @@ \snippet code/doc_src_properties.cpp 1 + Here is an example showing how to export member variables as Qt + properties using the \c MEMBER keyword. + Note that a \c NOTIFY signal must be specified to allow QML property bindings. + + \snippet code/doc_src_properties.cpp 8 + A property behaves like a class data member, but it has additional features accessible through the \l {Meta-Object System}. - \list + \list - \li A \c READ accessor function is required. It is for reading the - property value. Ideally, a const function is used for this purpose, - and it must return either the property's type or a pointer or - reference to that type. e.g., QWidget::focus is a read-only property - with \c READ function, QWidget::hasFocus(). + \li A \c READ accessor function is required if no \c MEMBER variable was + specified. It is for reading the property value. Ideally, a const function + is used for this purpose, and it must return either the property's type or a + pointer or reference to that type. e.g., QWidget::focus is a read-only + property with \c READ function, QWidget::hasFocus(). \li A \c WRITE accessor function is optional. It is for setting the property value. It must return void and must take exactly one @@ -71,6 +77,13 @@ QWidget::setEnabled(). Read-only properties do not need \c WRITE functions. e.g., QWidget::focus has no \c WRITE function. + \li A \c MEMBER variable association is required if no \c READ accessor + function is specified. This makes the given member variable + readable and writable without the need of creating \c READ and \c WRITE accessor + functions. It's still possible to use \c READ or \c WRITE accessor functions in + addition to \c MEMBER variable association (but not both), if you need to + control the variable access. + \li A \c RESET function is optional. It is for setting the property back to its context specific default value. e.g., QWidget::cursor has the typical \c READ and \c WRITE functions, QWidget::cursor() @@ -82,10 +95,14 @@ \li A \c NOTIFY signal is optional. If defined, it should specify one existing signal in that class that is emitted whenever the value of the property changes. + \c NOTIFY signals for \c MEMBER variables must take zero or one parameter, + which must be of the same type as the property. The parameter will take the + new value of the property. \li A \c REVISION number is optional. If included, it defines the property and its notifier signal to be used in a particular - revision of the API that is exposed to QML. + revision of the API (usually for exposure to QML). If not included, it + defaults to 0. \li The \c DESIGNABLE attribute indicates whether the property should be visible in the property editor of GUI design tool (e.g., @@ -114,7 +131,7 @@ gets and sets a widget's \c USER property. \li The presence of the \c CONSTANT attibute indicates that the property - value is constant. For a given object instance, the READ method of a + value is constant. For a given object instance, the READ method of a constant property must return the same value every time it is called. This constant value may be different for different instances of the object. A constant property cannot have a WRITE method or a NOTIFY signal. @@ -256,7 +273,7 @@ Q_DECLARE_METATYPE() macro so that their values can be stored in QVariant objects. This makes them suitable for use with both static properties declared using the Q_PROPERTY() macro in class - definitions and dynamic properties created at run-time. + definitions and dynamic properties created at run-time. \sa Q_DECLARE_METATYPE(), QMetaType, QVariant |