QProperty Class

Member Function Documentation

Assigns newValue to this property and removes the property's associated binding, if present.

Assigns newValue to this property and returns a reference to this QProperty.

QProperty::QProperty()

Constructs a property with a default constructed instance of T.

[explicit] template <typename Functor> QProperty::QProperty(Functor &&f)

Constructs a property that is tied to the provided binding expression f. The property's value is set to the result of evaluating the new binding. Whenever a dependency of the binding changes, the binding will be re-evaluated, and the property's value gets updated accordingly.

[explicit default] QProperty::QProperty(T &&initialValue)

Move-Constructs a property with the provided initialValue.

[explicit] QProperty::QProperty(const QPropertyBinding<T> &binding)

Constructs a property that is tied to the provided binding expression. The property's value is set to the result of evaluating the new binding. Whenever a dependency of the binding changes, the binding will be re-evaluated, and the property's value gets updated accordingly.

[explicit default] QProperty::QProperty(const T &initialValue)

Constructs a property with the provided initialValue.

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 property's value is set to the result of evaluating the new binding. Whenever a dependency of the binding changes, the binding will be re-evaluated, and the property's value gets updated accordingly.

See also binding().

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 property's value is set to the result of evaluating the new binding. Whenever a dependency of the binding changes, the binding will be re-evaluated, and the property's value gets updated accordingly.

See also Formulating a Property Binding.

bool QProperty::setBinding(const QUntypedPropertyBinding &newBinding)

This is an overloaded function.

Associates the value of this property with the provided newBinding expression. The property's value is set to the result of evaluating the new binding. Whenever a dependency of the binding changes, the binding will be re-evaluated, and the property's value gets updated accordingly.

Returns true if the type of this property is the same as the type the binding function returns; false otherwise.

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<T>::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().