Qt Documentation

Qt 5.14
Qt QML
Extending QML - Extension Objects Example

Extending QML - Extension Objects Example

Extension Objects.

This example builds on:

Extending QML - Adding Types Example

Shows how to use qmlRegisterExtendedType() 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 QLineEdit:

    qmlRegisterExtendedType<QLineEdit, LineEditExtension>("People", 1,0, "QLineEdit");

The QML engine then instantiates a QLineEdit:

    QQmlEngine engine;
    QQmlComponent component(&engine, QUrl("qrc:example.qml"));
    auto *edit = qobject_cast<QLineEdit *>(component.create());

In QML, a property is set on the line edit that only exists in the LineEditExtension class:

QLineEdit {
    leftMargin: 20
}

The extension type performs calls on the QLineEdit that otherwise will not be accessible to the QML engine.

Example project @ code.qt.io

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