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Extending QML - Extension Objects Example
=========================================
This example builds on the the :ref:`example_qml_tutorials_extending-qml-advanced_adding`.
Shows how to use :deco:`~PySide6.QtQml.QmlExtended` to provide an extension object to a
QLineEdit without modifying or subclassing it.
Firstly, the LineEditExtension class is registered with the QML system as an
extension of :class:`~PySide6.QtWidgets.QLineEdit`. We declare a foreign type to do
this as we cannot modify Qt's internal QLineEdit class.
.. code-block:: python
@QmlNamedElement("QLineEdit")
@QmlExtended(LineEditExtension)
@QmlForeign(QLineEdit)
class LineEditForeign(QObject):
Note the usage of :deco:`~PySide6.QtQml.QmlNamedElement` instead of
:deco:`~PySide6.QtQml.QmlElement`.
``QmlElement()`` uses the name of the containing type by default,
``LineEditExtension`` in this case. As the class being an extension class is
an implementation detail, we choose the more natural name ``QLineEdit``
instead.
The QML engine then instantiates a QLineEdit.
In QML, a property is set on the line edit that only exists in the
``LineEditExtension`` class:
.. code-block:: javascript
QLineEdit {
left_margin: 20
}
The extension type performs calls on the ``QLineEdit`` that otherwise will not
be accessible to the QML engine.
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