QBindable 类

template <typename T> class QBindable

QBindable 是围绕启用绑定特性的包裹器类。它允许类型安全操作，同时抽象出各种特性类之间的差异。更多...

头：	#include <QBindable>
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core
继承：	QUntypedBindable

所有成员列表，包括继承成员

公共函数

	QBindable (QObject * obj , const QMetaProperty & property )
	QBindable (QObject * obj , const char * property )
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

详细描述

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

另请参阅 QMetaProperty::isBindable , QProperty , QObjectBindableProperty , QObjectComputedProperty ，和 Qt Bindable Properties .

成员函数文档编制

`[explicit]` QBindable:: QBindable ( QObject * obj , const QMetaProperty & property )

见 QBindable::QBindable (QObject *obj, const char *property)

`[explicit]` QBindable:: QBindable ( QObject * obj , const char * property )

Constructs a QBindable for the 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 对于 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 QProperty or QObjectBindableProperty .

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

另请参阅 QProperty , QObjectBindableProperty ，和 Qt Bindable Properties .

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.

另请参阅 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 是只读或无效。

另请参阅 binding , isReadOnly ()，和 isValid ().

template <typename Functor> QPropertyBinding < T > QBindable:: setBinding ( Functor f )

这是重载函数。

创建 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 是只读或无效。

另请参阅 value (), isValid (), isReadOnly ()，和 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.

另请参阅 binding , setBinding ，和 hasBinding .

T QBindable:: value () const

Returns the underlying property's current value. If the QBindable is invalid, a default constructed T 被返回。

另请参阅 setValue () 和 isValid ().