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Diffstat (limited to 'src/corelib/doc/src/objectmodel/properties.qdoc')
| -rw-r--r-- | src/corelib/doc/src/objectmodel/properties.qdoc | 40 |
1 files changed, 22 insertions, 18 deletions
diff --git a/src/corelib/doc/src/objectmodel/properties.qdoc b/src/corelib/doc/src/objectmodel/properties.qdoc index eef2df7028..0e66c8445c 100644 --- a/src/corelib/doc/src/objectmodel/properties.qdoc +++ b/src/corelib/doc/src/objectmodel/properties.qdoc @@ -5,7 +5,7 @@ \page properties.html \title The Property System \brief An overview of Qt's property system. - + \ingroup explanations-basics \ingroup qt-basic-concepts \keyword Qt's Property System @@ -93,7 +93,7 @@ \li The \c DESIGNABLE attribute indicates whether the property should be visible in the property editor of GUI design tool (e.g., - \l {Qt Designer Manual}{Qt Designer}). Most properties are \c DESIGNABLE + \l {Qt Widgets Designer Manual}{\QD}). Most properties are \c DESIGNABLE (default true). Valid values are true and false. \li The \c SCRIPTABLE attribute indicates whether this property @@ -186,12 +186,11 @@ \section1 A Simple Example - Suppose we have a class MyClass, which is derived from QObject and - which uses the Q_OBJECT macro in its private section. We want to - declare a property in MyClass to keep track of a priority - value. The name of the property will be \e priority, and its type - will be an enumeration type named \e Priority, which is defined in - MyClass. + Suppose we have a class \c MyClass, which is derived from QObject and which + uses the Q_OBJECT macro. We want to declare a property in \c MyClass to keep + track of a priority value. The name of the property will be \c priority, and + its type will be an enumeration type named \c Priority, which is defined in + \c MyClass. We declare the property with the Q_PROPERTY() macro in the private section of the class. The required \c READ function is named \c @@ -200,7 +199,7 @@ System} using the Q_ENUM() macro. Registering an enumeration type makes the enumerator names available for use in calls to QObject::setProperty(). We must also provide our own declarations - for the \c READ and \c WRITE functions. The declaration of MyClass + for the \c READ and \c WRITE functions. The declaration of \c MyClass then might look like this: \snippet code/doc_src_properties.cpp 5 @@ -208,26 +207,29 @@ The \c READ function is const and returns the property type. The \c WRITE function returns void and has exactly one parameter of the property type. The meta-object compiler enforces these - requirements. + requirements. The equality check in the \c WRITE function, while not + mandatory, is good practice as there is no point in notifying and + potentially forcing re-evaluation in other places if nothing has + changed. - Given a pointer to an instance of MyClass or a pointer to a - QObject that is an instance of MyClass, we have two ways to set + Given a pointer to an instance of \c MyClass or a pointer to a + QObject that is an instance of \c MyClass, we have two ways to set its priority property: \snippet code/doc_src_properties.cpp 6 In the example, the enumeration type that is the property type is - declared in MyClass and registered with the \l{Meta-Object System} + declared in \c MyClass and registered with the \l{Meta-Object System} using the Q_ENUM() macro. This makes the enumeration values - available as strings for use as in the call to \l{QObject::}{setProperty()}. Had - the enumeration type been declared in another class, its fully + available as strings for use as in the call to \l{QObject::}{setProperty()}. + Had the enumeration type been declared in another class, its fully qualified name (i.e., OtherClass::Priority) would be required, and that other class would also have to inherit QObject and register the enumeration type there using the Q_ENUM() macro. A similar macro, Q_FLAG(), is also available. Like Q_ENUM(), it registers an enumeration type, but it marks the type as being a - set of \e flags, i.e. values that can be OR'd together. An I/O + set of \e flags, i.e., values that can be OR'd together. An I/O class might have enumeration values \c Read and \c Write and then QObject::setProperty() could accept \c{Read | Write}. Q_FLAG() should be used to register this enumeration type. @@ -274,7 +276,9 @@ Connected to the property system is an additional macro, Q_CLASSINFO(), that can be used to attach additional - \e{name}--\e{value} pairs to a class's meta-object, for example: + \e{name}--\e{value} pairs to a class's meta-object. This is + used for instance to mark a property as the \e default one + in the context of \l{QML Object Types}: \snippet code/doc_src_properties.cpp 7 @@ -296,5 +300,5 @@ and the general tips on implementing and using \l {Qt Bindable Properties}{bindable properties}. - \sa {Qt Bindable Properties} + \sa {Qt Bindable Properties}, {Defining QML Types from C++} */ |