QQmlContext Class

QQmlEngine engine;
QStringListModel modelData;
QQmlContext *context = new QQmlContext(engine.rootContext());
context->setContextProperty("myModel", &modelData);

QQmlComponent component(&engine);
component.setData("import QtQuick 2.0; ListView { model: myModel }", QUrl());
QObject *window = component.create(context);

class MyDataSet : public QObject {
    // ...
    Q_PROPERTY(QAbstractItemModel *myModel READ model NOTIFY modelChanged)
    // ...
};

MyDataSet myDataSet;
QQmlEngine engine;
QQmlContext *context = new QQmlContext(engine.rootContext());
context->setContextObject(&myDataSet);

QQmlComponent component(&engine);
component.setData("import QtQuick 2.0; ListView { model: myModel }", QUrl());
component.create(context);

QQmlEngine engine;
QQmlContext *context1 = new QQmlContext(engine.rootContext());
QQmlContext *context2 = new QQmlContext(context1);

context1->setContextProperty("a", 9001);
context1->setContextProperty("b", 9001);

context2->setContextProperty("b", 42);

Member Function Documentation

QQmlContext::QQmlContext(QQmlContext *parentContext, QObject *parent = nullptr)

Create a new QQmlContext with the given parentContext, and the QObject parent.

QQmlContext::QQmlContext(QQmlEngine *engine, QObject *parent = nullptr)

Create a new QQmlContext as a child of engine's root context, and the QObject parent.

[override virtual] QQmlContext::~QQmlContext()

Destroys the QQmlContext.

Any expressions, or sub-contexts dependent on this context will be invalidated, but not destroyed (unless they are parented to the QQmlContext object).

QUrl QQmlContext::baseUrl() const

Returns the base url of the component, or the containing component if none is set.

See also setBaseUrl().

QObject *QQmlContext::contextObject() const

Return the context object, or nullptr if there is no context object.

See also setContextObject().

QVariant QQmlContext::contextProperty(const QString &name) const

Returns the value of the name property for this context as a QVariant. If you know that the property you're looking for is a QObject assigned using a QML id in the current context, objectForName() is more convenient and faster. In contrast to objectForName() and nameForObject(), this method does traverse the context hierarchy and searches in parent contexts if the name is not found in the current one. It also considers any contextObject() you may have set.

See also setContextProperty(), objectForName(), nameForObject(), and contextObject().

QQmlEngine *QQmlContext::engine() const

Return the context's QQmlEngine, or nullptr if the context has no QQmlEngine or the QQmlEngine was destroyed.

bool QQmlContext::isValid() const

Returns whether the context is valid.

To be valid, a context must have a engine, and it's contextObject(), if any, must not have been deleted.

QString QQmlContext::nameForObject(const QObject *object) const

Returns the name of object in this context, or an empty string if object is not named in the context. Objects are named by setContextProperty(), or as properties of a context object, or by ids in the case of QML created contexts.

If the object has multiple names, the first is returned.

In contrast to contextProperty(), this method does not traverse the context hierarchy. If the name is not found in the current context, an empty String is returned.

See also contextProperty() and objectForName().

[since 6.2] QObject *QQmlContext::objectForName(const QString &name) const

Returns the object for a given name in this context. Returns nullptr if name is not available in the context or if the value associated with name is not a QObject. Objects are named by setContextProperty(), or as properties of a context object, or by ids in the case of QML created contexts. In contrast to contextProperty(), this method does not traverse the context hierarchy. If the name is not found in the current context, nullptr is returned.

This function was introduced in Qt 6.2.

See also contextProperty() and nameForObject().

QQmlContext *QQmlContext::parentContext() const

Return the context's parent QQmlContext, or nullptr if this context has no parent or if the parent has been destroyed.

QUrl QQmlContext::resolvedUrl(const QUrl &src) const

Resolves the URL src relative to the URL of the containing component.

See also QQmlEngine::baseUrl() and setBaseUrl().

void QQmlContext::setBaseUrl(const QUrl &baseUrl)

Explicitly sets the url resolvedUrl() will use for relative references to baseUrl.

Calling this function will override the url of the containing component used by default.

See also baseUrl() and resolvedUrl().

void QQmlContext::setContextObject(QObject *object)

Set the context object.

See also contextObject().

[since 5.11] void QQmlContext::setContextProperties(const QList<QQmlContext::PropertyPair> &properties)

Set a batch of properties on this context.

Setting all properties in one batch avoids unnecessary refreshing expressions, and is therefore recommended instead of calling setContextProperty() for each individual property.

This function was introduced in Qt 5.11.

See also QQmlContext::setContextProperty().

void QQmlContext::setContextProperty(const QString &name, QObject *value)

Set the value of the name property on this context.

QQmlContext does not take ownership of value.

See also contextProperty().

void QQmlContext::setContextProperty(const QString &name, const QVariant &value)

Set a the value of the name property on this context.