QProperty Class
template <typename T> class QPropertyThe QProperty class is a template class that enables automatic property bindings. More...
| Header: | #include <QProperty> |
| CMake: | find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
| Since: | Qt 6.0 |
| Inherits: | QPropertyData |
Public Functions
| QProperty(T &&initialValue) | |
| QProperty(const T &initialValue) | |
| QProperty(Functor &&f) | |
| QProperty(const QPropertyBinding<T> &binding) | |
| QProperty() | |
| QProperty<T> & | operator=(const QPropertyBinding<T> &newBinding) |
| ~QProperty() | |
| QPropertyNotifier | addNotifier(Functor f) |
| QPropertyBinding<T> | binding() const |
| QPropertyChangeHandler<Functor> | onValueChanged(Functor f) |
| QPropertyBinding<T> | setBinding(const QPropertyBinding<T> &newBinding) |
| bool | setBinding(const QUntypedPropertyBinding &newBinding) |
| QPropertyBinding<T> | setBinding(Functor f) |
| void | setValue(QProperty::rvalue_ref newValue) |
| void | setValue(QProperty::parameter_type newValue) |
| QPropertyChangeHandler<Functor> | subscribe(Functor f) |
| QPropertyBinding<T> | takeBinding() |
| QProperty::parameter_type | value() const |
| QProperty<T> & | operator=(QProperty::rvalue_ref newValue) |
| QProperty<T> & | operator=(QProperty::parameter_type newValue) |
Detailed Description
QProperty<T> is one of the classes implementing Qt Bindable Properties. It is a container that holds an instance of T. You can assign a value to it and you can read it via the value() function or the T conversion operator. You can also tie the property to an expression that computes the value dynamically, the binding expression. It is represented as a C++ lambda and can be used to express relationships between different properties in your application.
Member Function Documentation
QProperty<T> &QProperty::operator=(QProperty::parameter_type newValue)
QProperty<T> &QProperty::operator=(QProperty::rvalue_ref newValue)
Assigns newValue to this property and returns a reference to this QProperty.
void QProperty::setValue(QProperty::parameter_type newValue)
void QProperty::setValue(QProperty::rvalue_ref newValue)
Assigns newValue to this property and removes the property's associated binding, if present.
[default] QProperty::QProperty(T &&initialValue)
Move-Constructs a property with the provided initialValue.
[default] QProperty::QProperty(const T &initialValue)
Constructs a property with the provided initialValue.
template <typename Functor> QProperty::QProperty(Functor &&f)
Constructs a property that is tied to the provided binding expression f. The first time the property value is read, the binding is evaluated. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
QProperty::QProperty(const QPropertyBinding<T> &binding)
Constructs a property that is tied to the provided binding expression. The first time the property value is read, the binding is evaluated. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
QProperty::QProperty()
Constructs a property with a default constructed instance of T.
[default] QProperty<T> &QProperty::operator=(const QPropertyBinding<T> &newBinding)
Associates the value of this property with the provided newBinding expression and returns a reference to this property. The first time the property value is read, the binding is evaluated. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
QProperty::~QProperty()
Destroys the property.
template <typename Functor> QPropertyNotifier QProperty::addNotifier(Functor f)
Subscribes the given functor f as a callback that is called whenever the value of the property changes.
The callback f is expected to be a type that has a plain call operator () without any parameters. This means that you can provide a C++ lambda expression, a std::function or even a custom struct with a call operator.
The returned property change handler object keeps track of the subscription. When it goes out of scope, the callback is unsubscribed.
This method is in some cases easier to use than onValueChanged(), as the returned object is not a template. It can therefore more easily be stored, e.g. as a member in a class.
See also onValueChanged() and subscribe().
QPropertyBinding<T> QProperty::binding() const
Returns the binding expression that is associated with this property. A default constructed QPropertyBinding<T> will be returned if no such association exists.
See also setBinding().
template <typename Functor> QPropertyChangeHandler<Functor> QProperty::onValueChanged(Functor f)
Registers the given functor f as a callback that shall be called whenever the value of the property changes. On each value change, the handler is either called immediately, or deferred, depending on the context.
The callback f is expected to be a type that has a plain call operator () without any parameters. This means that you can provide a C++ lambda expression, a std::function or even a custom struct with a call operator.
The returned property change handler object keeps track of the registration. When it goes out of scope, the callback is de-registered.
QPropertyBinding<T> QProperty::setBinding(const QPropertyBinding<T> &newBinding)
Associates the value of this property with the provided newBinding expression and returns the previously associated binding. The first time the property value is read, the binding is evaluated. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
See also binding().
bool QProperty::setBinding(const QUntypedPropertyBinding &newBinding)
This is an overloaded function.
Associates the value of this property with the provided newBinding expression. The first time the property value is read, the binding is evaluated. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
Returns true if the type of this property is the same as the type the binding function returns; false otherwise.
template <typename Functor> QPropertyBinding<T> QProperty::setBinding(Functor f)
This is an overloaded function.
Associates the value of this property with the provided functor f and returns the previously associated binding. The first time the property value is read, the binding is evaluated by invoking the call operator () of f. Whenever a dependency of the binding changes, the binding will be re-evaluated the next time the value of this property is read.
See also Formulating a Property Binding.
template <typename Functor> QPropertyChangeHandler<Functor> QProperty::subscribe(Functor f)
Subscribes the given functor f as a callback that is called immediately and whenever the value of the property changes in the future. On each value change, the handler is either called immediately, or deferred, depending on the context.
The callback f is expected to be a type that can be copied and has a plain call operator() without any parameters. This means that you can provide a C++ lambda expression, a std::function or even a custom struct with a call operator.
The returned property change handler object keeps track of the subscription. When it goes out of scope, the callback is unsubscribed.
QPropertyBinding<T> QProperty::takeBinding()
Disassociates the binding expression from this property and returns it. After calling this function, the value of the property will only change if you assign a new value to it, or when a new binding is set.
QProperty::parameter_type QProperty::value() const
Returns the value of the property. This may evaluate a binding expression that is tied to this property, before returning the value.
See also setValue().