Contents

• Public Types
• Public Functions
• Static Public Members
• Detailed Description

Detailed Description

TheQDeclarativeProperty class abstracts accessing properties on objects created from QML.

As QML uses Qt's meta-type system all of the existingQMetaObject classes can be used to introspect and interact with objects created by QML. However, some of the new features provided by QML - such as type safety and attached properties - are most easily used through theQDeclarativeProperty class that simplifies some of their natural complexity.

UnlikeQMetaProperty which represents a property on a class type,QDeclarativeProperty encapsulates a property on a specific object instance. To read a property's value, programmers create aQDeclarativeProperty instance and call theread() method. Likewise to write a property value thewrite() method is used.

For example, for the following QML code:

// MyItem.qmlimport QtQuick 1.0Text {text:"A bit of text" }

TheText object's properties could be accessed usingQDeclarativeProperty, like this:

#include <QDeclarativeProperty>#include <QGraphicsObject>...QDeclarativeView view(QUrl::fromLocalFile("MyItem.qml"));QDeclarativePropertyproperty(view.rootObject(),"font.pixelSize");qWarning()<<"Current pixel size:"<< property.read().toInt();property.write(24);qWarning()<<"Pixel size should now be 24:"<< property.read().toInt();

Member Type Documentation

enum QDeclarativeProperty::PropertyTypeCategory

This enum specifies a category of QML property.

enum QDeclarativeProperty::Type

This enum specifies a type of QML property.

Member Function Documentation

QDeclarativeProperty::QDeclarativeProperty()

Create an invalidQDeclarativeProperty.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj)

Creates aQDeclarativeProperty for the default property ofobj. If there is no default property, an invalidQDeclarativeProperty will be created.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj,QDeclarativeContext * ctxt)

Creates aQDeclarativeProperty for the default property ofobj using thecontextctxt. If there is no default property, an invalidQDeclarativeProperty will be created.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj,QDeclarativeEngine * engine)

Creates aQDeclarativeProperty for the default property ofobj using the environment for instantiating QML components that is provided byengine. If there is no default property, an invalidQDeclarativeProperty will be created.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj, constQString & name)

Creates aQDeclarativeProperty for the propertyname ofobj.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj, constQString & name,QDeclarativeContext * ctxt)

Creates aQDeclarativeProperty for the propertyname ofobj using thecontextctxt.

Creating aQDeclarativeProperty without a context will render some properties - like attached properties - inaccessible.

QDeclarativeProperty::QDeclarativeProperty(QObject * obj, constQString & name,QDeclarativeEngine * engine)

Creates aQDeclarativeProperty for the propertyname ofobj using the environment for instantiating QML components that is provided byengine.

QDeclarativeProperty::QDeclarativeProperty(constQDeclarativeProperty & other)

Create a copy ofother.

bool QDeclarativeProperty::connectNotifySignal(QObject * dest, constchar * slot) const

Connects the property's change notifier signal to the specifiedslot of thedest object and returns true. Returns false if this metaproperty does not represent a regular Qt property or if it has no change notifier signal, or if thedest object does not have the specifiedslot.

bool QDeclarativeProperty::connectNotifySignal(QObject * dest,int method) const

Connects the property's change notifier signal to the specifiedmethod of thedest object and returns true. Returns false if this metaproperty does not represent a regular Qt property or if it has no change notifier signal, or if thedest object does not have the specifiedmethod.

bool QDeclarativeProperty::hasNotifySignal() const

Returns true if the property has a change notifier signal, otherwise false.

int QDeclarativeProperty::index() const

Return the Qt metaobject index of the property.

bool QDeclarativeProperty::isDesignable() const

Returns true if the property is designable, otherwise false.

bool QDeclarativeProperty::isProperty() const

Returns true if thisQDeclarativeProperty represents a regular Qt property.

bool QDeclarativeProperty::isResettable() const

Returns true if the property is resettable, otherwise false.

bool QDeclarativeProperty::isSignalProperty() const

Returns true if thisQDeclarativeProperty represents a QML signal property.

bool QDeclarativeProperty::isValid() const

Returns true if theQDeclarativeProperty refers to a valid property, otherwise false.

bool QDeclarativeProperty::isWritable() const

Returns true if the property is writable, otherwise false.

QMetaMethod QDeclarativeProperty::method() const

Return theQMetaMethod for this property if it is aSignalProperty, otherwise returns an invalidQMetaMethod.

QString QDeclarativeProperty::name() const

Return the name of this QML property.

bool QDeclarativeProperty::needsNotifySignal() const

Returns true if the property needs a change notifier signal for bindings to remain upto date, false otherwise.

Some properties, such as attached properties or those whose value never changes, do not require a change notifier.

QObject * QDeclarativeProperty::object() const

Returns theQDeclarativeProperty'sQObject.

QMetaProperty QDeclarativeProperty::property() const

Returns theQt property associated with this QML property.

int QDeclarativeProperty::propertyType() const

Returns theQVariant type of the property, orQVariant::Invalid if the property has noQVariant type.

PropertyTypeCategory QDeclarativeProperty::propertyTypeCategory() const

Returns the property category.

constchar * QDeclarativeProperty::propertyTypeName() const

Returns the type name of the property, or 0 if the property has no type name.

QVariant QDeclarativeProperty::read() const

Returns the property value.

[static]QVariant QDeclarativeProperty::read(QObject * object, constQString & name)

Return thename property value ofobject. This method is equivalent to:

QDeclarativeProperty p(object, name);p.read();

[static]QVariant QDeclarativeProperty::read(QObject * object, constQString & name,QDeclarativeContext * ctxt)

Return thename property value ofobject using thecontextctxt. This method is equivalent to:

QDeclarativeProperty p(object, name, context);p.read();

[static]QVariant QDeclarativeProperty::read(QObject * object, constQString & name,QDeclarativeEngine * engine)

Return thename property value ofobject using the environment for instantiating QML components that is provided byengine. . This method is equivalent to:

QDeclarativeProperty p(object, name, engine);p.read();

bool QDeclarativeProperty::reset() const

Resets the property and returns true if the property is resettable. If the property is not resettable, nothing happens and false is returned.

Type QDeclarativeProperty::type() const

Returns the type of the property.

bool QDeclarativeProperty::write(constQVariant & value) const

Sets the property value tovalue and returns true. Returns false if the property can't be set because thevalue is the wrong type, for example.

[static]bool QDeclarativeProperty::write(QObject * object, constQString & name, constQVariant & value)

Writesvalue to thename property ofobject. This method is equivalent to:

QDeclarativeProperty p(object, name);p.write(value);

[static]bool QDeclarativeProperty::write(QObject * object, constQString & name, constQVariant & value,QDeclarativeContext * ctxt)

Writesvalue to thename property ofobject using thecontextctxt. This method is equivalent to:

QDeclarativeProperty p(object, name, ctxt);p.write(value);

[static]bool QDeclarativeProperty::write(QObject * object, constQString & name, constQVariant & value,QDeclarativeEngine * engine)

Writesvalue to thename property ofobject using the environment for instantiating QML components that is provided byengine. This method is equivalent to:

QDeclarativeProperty p(object, name, engine);p.write(value);

QDeclarativeProperty & QDeclarativeProperty::operator=(constQDeclarativeProperty & other)

Assignother to thisQDeclarativeProperty.

bool QDeclarativeProperty::operator==(constQDeclarativeProperty & other) const

Returns true ifother and thisQDeclarativeProperty represent the same property.