QDeclarativeProperty Class ReferenceThe QDeclarativeProperty class abstracts accessing properties on objects created from QML. More... #include <QDeclarativeProperty> This class was introduced in Qt 4.7. Public Types
Public Functions
Static Public Members
Detailed DescriptionThe QDeclarativeProperty class abstracts accessing properties on objects created from QML. As QML uses Qt's meta-type system all of the existing QMetaObject 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 the QDeclarativeProperty class that simplifies some of their natural complexity. Unlike QMetaProperty 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 a QDeclarativeProperty instance and call the read() method. Likewise to write a property value the write() method is used. For example, for the following QML code: // MyItem.qml import QtQuick 1.0 Text { text: "A bit of text" } The Text object's properties could be accessed using QDeclarativeProperty, like this: #include <QDeclarativeProperty> #include <QGraphicsObject> ... QDeclarativeView view(QUrl::fromLocalFile("MyItem.qml")); QDeclarativeProperty property(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
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Constant | Value | Description |
---|---|---|
QDeclarativeProperty::InvalidCategory | 0 | The property is invalid, or is a signal property. |
QDeclarativeProperty::List | 1 | The property is a QDeclarativeListProperty list property |
QDeclarativeProperty::Object | 2 | The property is a QObject derived type pointer |
QDeclarativeProperty::Normal | 3 | The property is a normal value property. |
This enum specifies a type of QML property.
Constant | Value | Description |
---|---|---|
QDeclarativeProperty::Invalid | 0 | The property is invalid. |
QDeclarativeProperty::Property | 1 | The property is a regular Qt property. |
QDeclarativeProperty::SignalProperty | 2 | The property is a signal property. |
Create an invalid QDeclarativeProperty.
Creates a QDeclarativeProperty for the default property of obj. If there is no default property, an invalid QDeclarativeProperty will be created.
Creates a QDeclarativeProperty for the default property of obj using the context ctxt. If there is no default property, an invalid QDeclarativeProperty will be created.
Creates a QDeclarativeProperty for the default property of obj using the environment for instantiating QML components that is provided by engine. If there is no default property, an invalid QDeclarativeProperty will be created.
Creates a QDeclarativeProperty for the property name of obj.
Creates a QDeclarativeProperty for the property name of obj using the context ctxt.
Creating a QDeclarativeProperty without a context will render some properties - like attached properties - inaccessible.
Creates a QDeclarativeProperty for the property name of obj using the environment for instantiating QML components that is provided by engine.
Create a copy of other.
Connects the property's change notifier signal to the specified slot of the dest 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 the dest object does not have the specified slot.
Connects the property's change notifier signal to the specified method of the dest 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 the dest object does not have the specified method.
Returns true if the property has a change notifier signal, otherwise false.
Return the Qt metaobject index of the property.
Returns true if the property is designable, otherwise false.
Returns true if this QDeclarativeProperty represents a regular Qt property.
Returns true if the property is resettable, otherwise false.
Returns true if this QDeclarativeProperty represents a QML signal property.
Returns true if the QDeclarativeProperty refers to a valid property, otherwise false.
Returns true if the property is writable, otherwise false.
Return the QMetaMethod for this property if it is a SignalProperty, otherwise returns an invalid QMetaMethod.
Return the name of this QML property.
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.
Returns the QDeclarativeProperty's QObject.
Returns the Qt property associated with this QML property.
Returns the QVariant type of the property, or QVariant::Invalid if the property has no QVariant type.
Returns the property category.
Returns the type name of the property, or 0 if the property has no type name.
Returns the property value.
Return the name property value of object. This method is equivalent to:
QDeclarativeProperty p(object, name); p.read();
Return the name property value of object using the context ctxt. This method is equivalent to:
QDeclarativeProperty p(object, name, context); p.read();
Return the name property value of object using the environment for instantiating QML components that is provided by engine. . This method is equivalent to:
QDeclarativeProperty p(object, name, engine); p.read();
Resets the property and returns true if the property is resettable. If the property is not resettable, nothing happens and false is returned.
Returns the type of the property.
Sets the property value to value and returns true. Returns false if the property can't be set because the value is the wrong type, for example.
Writes value to the name property of object. This method is equivalent to:
QDeclarativeProperty p(object, name); p.write(value);
Writes value to the name property of object using the context ctxt. This method is equivalent to:
QDeclarativeProperty p(object, name, ctxt); p.write(value);
Writes value to the name property of object using the environment for instantiating QML components that is provided by engine. This method is equivalent to:
QDeclarativeProperty p(object, name, engine); p.write(value);
Assign other to this QDeclarativeProperty.
Returns true if other and this QDeclarativeProperty represent the same property.
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