QQmlComponent

QQmlComponent is a class in the Qt QML framework that represents a QML component as loaded from a source and ready to be instantiated. It belongs to the QtQml module and is used to load, compile and create QML objects at runtime. A component can be created with a reference to a QQmlEngine or as a QObject, and it can load QML from a URL or from inline data. Source can be provided via setSource(QUrl) or setData(const QByteArray& data, bool isFromFile). The URL identifies the QML file, while the data string contains the QML code. The component maintains a status via the Status enum: Null, Loading, Ready, and Error. The errors() function returns a list of QQmlError objects that describe syntax or runtime issues encountered during loading or parsing.

Once the component is Ready, instances can be created by calling create(QQmlContext*) which returns a pointer to the newly created QObject. The created object becomes part of the given QQmlContext; the component can be used to instantiate multiple objects. For asynchronous scenarios, QQmlComponent provides beginCreate and completeCreate to support staged creation.

If the component references other JavaScript types or modules, the loader resolves them using the associated QQmlEngine. The component’s lifecycle is tied to the engine; disposing the engine invalidates its components. Typical usage involves creating a component, loading its source, checking for errors, then creating objects and setting properties as needed.