QBindable Class
template <typename T> class QBindableQBindable is a wrapper class around binding-enabled properties. It allows type-safe operations while abstracting the differences between the various property classes away. More...
Header: | #include <QBindable> |
CMake: | find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core) |
qmake: | QT += core |
Inherits: | QUntypedBindable |
Public Functions
QPropertyBinding<T> | binding() const |
QPropertyBinding<T> | makeBinding(const QPropertyBindingSourceLocation &location = QT_PROPERTY_DEFAULT_BINDING_LOCATION) const |
QPropertyBinding<T> | setBinding(const QPropertyBinding<T> &binding) |
QPropertyBinding<T> | setBinding(Functor f) |
void | setValue(const T &value) |
QPropertyBinding<T> | takeBinding() |
T | value() const |
Detailed Description
QBindable<T> helps to integrate Qt's traditional Q_PROPERTY with binding-enabled properties. If a property is backed by a QProperty, QObjectBindableProperty or QObjectComputedProperty, you can add BINDABLE
bindablePropertyName to the Q_PROPERTY declaration, where bindablePropertyName is a function returning an instance of QBindable constructed from the QProperty. The returned QBindable allows users of the property to set and query bindings of the property, without having to know the exact kind of binding-enabled property used.
class MyClass : public QObject { Q_OBJECT Q_PROPERTY(int x READ x WRITE setX NOTIFY xChanged BINDABLE bindableX) public: int x() const { return xProp; } void setX(int x) { xProp = x; } QBindable<int> bindableX() { return QBindable<int>(&xProp); } signals: void xChanged(); private: // Declare the instance of the bindable property data. Q_OBJECT_BINDABLE_PROPERTY(MyClass, int, xProp, &MyClass::xChanged) }; MyClass *myObject; QBindable<int> bindableX = myObject->bindableX(); qDebug() << bindableX.hasBinding(); // prints false QProperty<int> y {42}; bindableX.setBinding([&](){ return 2*y.value(); }); qDebug() << bindableX.hasBinding() << myObject->x(); // prints true 84
See also QMetaProperty::isBindable, QProperty, QObjectBindableProperty, QObjectComputedProperty, and Qt Bindable Properties.
Member Function Documentation
QPropertyBinding<T> QBindable::binding() const
Returns the currently set binding of the underlying property. If the property does not have a binding, the returned QPropertyBinding<T>
will be invalid.
See also setBinding and hasBinding.
QPropertyBinding<T> QBindable::makeBinding(const QPropertyBindingSourceLocation &location = QT_PROPERTY_DEFAULT_BINDING_LOCATION) const
Constructs a binding evaluating to the underlying property's value, using a specified source location.
QPropertyBinding<T> QBindable::setBinding(const QPropertyBinding<T> &binding)
Sets the underlying property's binding to binding. Does nothing if the QBindable is read-only or invalid.
See also binding, isReadOnly(), and isValid().
template <typename Functor> QPropertyBinding<T> QBindable::setBinding(Functor f)
This is an overloaded function.
Creates a QPropertyBinding<T>
from f, and sets it as the underlying property's binding.
void QBindable::setValue(const T &value)
Sets the underlying property's value to value. This removes any currenltly set binding from it. This function has no effect if the QBindable is read-only or invalid.
See also value(), isValid(), isReadOnly(), and setBinding().
QPropertyBinding<T> QBindable::takeBinding()
Removes the currently set binding of the underlying property and returns it. If the property does not have a binding, the returned QPropertyBinding<T>
will be invalid.
See also binding, setBinding, and hasBinding.
T QBindable::value() const
Returns the underlying property's current value. If the QBindable is invalid, a default constructed T
is returned.
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