QBindable< T > Class Template Reference

\inmodule QtCore More...

#include <qproperty.h>

Inheritance diagram for QBindable< T >:

Collaboration diagram for QBindable< T >:

Public Member Functions
	QBindable (const QUntypedBindable &b)
	QBindable (QObject *obj, const QMetaProperty &property)
	See \l QBindable::QBindable(QObject *obj, const char *property)
	QBindable (QObject *obj, const char *property)
	Constructs a QBindable for the \l Q_PROPERTY property on obj.
QPropertyBinding< T >	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 >	binding () const
	Returns the currently set binding of the underlying property.
QPropertyBinding< T >	takeBinding ()
	Removes the currently set binding of the underlying property and returns it.
QPropertyBinding< T >	setBinding (const QPropertyBinding< T > &binding)
	Sets the underlying property's binding to binding.
template<typename Functor >
QPropertyBinding< T >	setBinding (Functor &&f, const QPropertyBindingSourceLocation &location=QT_PROPERTY_DEFAULT_BINDING_LOCATION, std::enable_if_t< std::is_invocable_v< Functor > > *=nullptr)
T	value () const
	Returns the underlying property's current value.
void	setValue (const T &value)
	Sets the underlying property's value to value.
constexpr	QUntypedBindable (QUntypedPropertyData *d, const QtPrivate::QBindableInterface *i)
Q_CORE_EXPORT	QUntypedBindable (QObject *obj, const QMetaProperty &property, const QtPrivate::QBindableInterface *i)
Q_CORE_EXPORT	QUntypedBindable (QObject *obj, const char *property, const QtPrivate::QBindableInterface *i)
constexpr	QUntypedBindable ()=default
	Default-constructs a QUntypedBindable.
template<typename Property >
	QUntypedBindable (Property *p)
	Constructs a QUntypedBindable from the property property.
bool	setBinding (const QUntypedPropertyBinding &binding)
	Sets the underlying property's binding to binding.
Public Member Functions inherited from QUntypedBindable
constexpr	QUntypedBindable ()=default
	Default-constructs a QUntypedBindable.
template<typename Property >
	QUntypedBindable (Property *p)
	Constructs a QUntypedBindable from the property property.
bool	isValid () const
	Returns true if the QUntypedBindable is valid.
bool	isBindable () const
bool	isReadOnly () const
QUntypedPropertyBinding	makeBinding (const QPropertyBindingSourceLocation &location=QT_PROPERTY_DEFAULT_BINDING_LOCATION) const
	Creates a binding returning the underlying properties' value, using a specified source location.
QUntypedPropertyBinding	takeBinding ()
	Removes the currently set binding from the property and returns it.
void	observe (QPropertyObserver *observer) const
template<typename Functor >
QPropertyChangeHandler< Functor >	onValueChanged (Functor f) const
	Installs f as a change handler.
template<typename Functor >
QPropertyChangeHandler< Functor >	subscribe (Functor f) const
	Behaves like a call to f followed by onValueChanged(f),.
template<typename Functor >
QPropertyNotifier	addNotifier (Functor f)
	Installs f as a change handler.
QUntypedPropertyBinding	binding () const
	Returns the underlying property's binding if there is any, or a default constructed QUntypedPropertyBinding otherwise.
bool	setBinding (const QUntypedPropertyBinding &binding)
	Sets the underlying property's binding to binding.
bool	hasBinding () const
	Returns true if the underlying property has a binding.
QMetaType	metaType () const

Friends
template<typename U >
class	QPropertyAlias

Additional Inherited Members
Protected Member Functions inherited from QUntypedBindable
constexpr	QUntypedBindable (QUntypedPropertyData *d, const QtPrivate::QBindableInterface *i)
Q_CORE_EXPORT	QUntypedBindable (QObject *obj, const QMetaProperty &property, const QtPrivate::QBindableInterface *i)
Q_CORE_EXPORT	QUntypedBindable (QObject *obj, const char *property, const QtPrivate::QBindableInterface *i)
Protected Attributes inherited from QUntypedBindable
QUntypedPropertyData *	data = nullptr
const QtPrivate::QBindableInterface *	iface = nullptr

Detailed Description

template<typename T>
class QBindable< T >

\inmodule QtCore

QBindable is a wrapper class around binding-enabled properties. It allows type-safe operations while abstracting the differences between the various property classes away. \inherits QUntypedBindable

QBindable<T> helps to integrate Qt's traditional Q_PROPERTY with \l {Qt Bindable Properties}{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, {Qt Bindable Properties}

Definition at line 808 of file qproperty.h.

Constructor & Destructor Documentation

QBindable() [1/3]

template<typename T >

QBindable< T >::QBindable ( const QUntypedBindable &  b )

inlineexplicit

Definition at line 817 of file qproperty.h.

References QUntypedBindable::iface, and QUntypedBindable::metaType().

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QBindable() [2/3]

template<typename T >

template< typename T > QBindable< T >::QBindable ( QObject *  obj, const QMetaProperty &  property  )

inlineexplicit

See \l QBindable::QBindable(QObject *obj, const char *property)

Definition at line 825 of file qproperty.h.

QBindable() [3/3]

template<typename T >

template< typename T > QBindable< T >::QBindable ( QObject *  obj, const char *  property  )

inlineexplicit

Constructs a QBindable for the \l Q_PROPERTY property on obj.

The property must have a notify signal but does not need to have BINDABLE in its Q_PROPERTY definition, so even binding unaware {Q_PROPERTY}s can be bound or used in binding expressions. You must use QBindable::value() in binding expressions instead of the normal property READ function (or MEMBER) to enable dependency tracking if the property is not BINDABLE. When binding using a lambda, you may prefer to capture the QBindable by value to avoid the cost of calling this constructor in the binding expression. This constructor should not be used to implement BINDABLE for a Q_PROPERTY, as the resulting Q_PROPERTY will not support dependency tracking. To make a property that is usable directly without reading through a QBindable use \l QProperty or \l QObjectBindableProperty.

QProperty<QString> displayText;
QDateTimeEdit *dateTimeEdit = findDateTimeEdit();
QBindable<QDateTime> dateTimeBindable(dateTimeEdit, "dateTime");
displayText.setBinding([dateTimeBindable](){ return dateTimeBindable.value().toString(); });

See also

QProperty, QObjectBindableProperty, {Qt Bindable Properties}

Definition at line 828 of file qproperty.h.

Member Function Documentation

binding()

template<typename T >

template< typename T > QPropertyBinding< T > QBindable< T >::binding ( ) const

inline

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, hasBinding !

QPropertyBinding::isValid()

Definition at line 835 of file qproperty.h.

References QUntypedBindable::binding().

Referenced by QBindable< T >::setBinding().

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makeBinding()

template<typename T >

template< typename T > QPropertyBinding< T > QBindable< T >::makeBinding ( const QPropertyBindingSourceLocation &  location = QT_PROPERTY_DEFAULT_BINDING_LOCATION ) const

inline

Constructs a binding evaluating to the underlying property's value, using a specified source location.

Definition at line 831 of file qproperty.h.

References QUntypedBindable::makeBinding().

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QUntypedBindable() [1/5]

template<typename T >

QUntypedBindable::QUntypedBindable ( )

constexprdefault

Default-constructs a QUntypedBindable.

It is in an invalid state.

See also

isValid()

QUntypedBindable() [2/5]

template<typename T >

template<typename Property >

template< typename Property > QUntypedBindable::QUntypedBindable ( Property *  property )

inline

Constructs a QUntypedBindable from the property property.

If Property is const, the QUntypedBindable will be read only. If property is null, the QUntypedBindable will be invalid.

See also

isValid(), isReadOnly()

Definition at line 692 of file qproperty.h.

QUntypedBindable() [3/5]

template<typename T >

QUntypedBindable::QUntypedBindable ( QObject *  obj, const char *  property, const QtPrivate::QBindableInterface *  i  )

explicit

Definition at line 687 of file qproperty.cpp.

QUntypedBindable() [4/5]

template<typename T >

QUntypedBindable::QUntypedBindable ( QObject *  obj, const QMetaProperty &  property, const QtPrivate::QBindableInterface *  i  )

explicit

Definition at line 686 of file qproperty.cpp.

QUntypedBindable() [5/5]

template<typename T >

constexpr QUntypedBindable::QUntypedBindable ( QUntypedPropertyData *  d, const QtPrivate::QBindableInterface *  i  )

inlineconstexpr

Definition at line 682 of file qproperty.h.

setBinding() [1/3]

template<typename T >

template< typename T > void QBindable< T >::setBinding ( const QPropertyBinding< T > &  binding )

inline

Sets the underlying property's binding to binding.

Does nothing if the QBindable is read-only or invalid.

See also

binding, isReadOnly(), isValid() !

QPropertyBinding::isValid()

Definition at line 846 of file qproperty.h.

References QBindable< T >::binding(), QUntypedBindable::iface, QtPrivate::BindableWarnings::InvalidInterface, QUntypedBindable::metaType(), QtPrivate::BindableWarnings::printUnsuitableBindableWarning(), Q_ASSERT, QtPrivate::BindableWarnings::ReadOnlyInterface, and QtPrivate::QBindableInterface::setBinding.

Referenced by Q_OBJECT_BINDABLE_PROPERTY_WITH_ARGS(), and QBindable< T >::setBinding().

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setBinding() [2/3]

template<typename T >

bool QUntypedBindable::setBinding ( const QUntypedPropertyBinding &  binding )

inline

Sets the underlying property's binding to binding.

This does not have any effect if the QUntypedBindable is read-only, null or if binding's type does match the underlying property's type.

Returns

true when the binding was successfully set.

!

See also

QUntypedPropertyBinding::valueMetaType()

Definition at line 766 of file qproperty.h.

setBinding() [3/3]

template<typename T >

template<typename Functor >

QPropertyBinding< T > QBindable< T >::setBinding ( Functor &&  f, const QPropertyBindingSourceLocation &  location = QT_PROPERTY_DEFAULT_BINDING_LOCATION, std::enable_if_t< std::is_invocable_v< Functor > > *  = nullptr  )

inline

Definition at line 862 of file qproperty.h.

References Qt::makePropertyBinding(), and QBindable< T >::setBinding().

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setValue()

template<typename T >

template< typename T > void QBindable< T >::setValue ( const T &  value )

inline

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

isValid(), isReadOnly(), setBinding()

Definition at line 883 of file qproperty.h.

References QUntypedBindable::iface, and QtPrivate::QBindableInterface::setter.

takeBinding()

template<typename T >

template< typename T > QPropertyBinding< T > QBindable< T >::takeBinding ( )

inline

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, hasBinding !

QPropertyBinding::isValid()

Definition at line 840 of file qproperty.h.

References QUntypedBindable::takeBinding().

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value()

template<typename T >

template< typename T > T QBindable< T >::value ( ) const

inline

Returns the underlying property's current value.

If the QBindable is invalid, a default constructed T is returned.

See also

isValid()

Definition at line 873 of file qproperty.h.

References QtPrivate::QBindableInterface::getter, and QUntypedBindable::iface.

Friends And Related Symbol Documentation

QPropertyAlias

template<typename T >

template<typename U >

friend class QPropertyAlias

friend

Definition at line 811 of file qproperty.h.

---

The documentation for this class was generated from the following files:

• qtbase/src/corelib/kernel/qobject.h
• qtbase/src/corelib/kernel/qproperty.h
• qtbase/src/corelib/kernel/qproperty.cpp