QIfAbstractFeature Class

Member Function Documentation

[explicit] QIfAbstractFeature::QIfAbstractFeature(const QString &interfaceName, QObject *parent = nullptr)

Constructs an abstract feature.

The parent argument is passed on to the QObject constructor.

The interfaceName argument is used to locate suitable service objects.

[virtual protected] bool QIfAbstractFeature::acceptServiceObject(QIfServiceObject *serviceObject)

This method is expected to be implemented by any class subclassing QIfAbstractFeature.

The method should return true if the given serviceObject is accepted and can be used, otherwise false.

If the object is accepted, connectToServiceObject is called to actually connect to the service object.

The default implementation accepts the serviceObject if it implements the interface returned by interfaceName();

See also connectToServiceObject(), disconnectFromServiceObject(), and clearServiceObject().

[pure virtual protected] void QIfAbstractFeature::clearServiceObject()

This method is expected to be implemented by any class subclassing QIfAbstractFeature.

Called when no service object is available. The implementation is expected to set all properties to safe defaults and forget all links to the previous service object.

There is no need to disconnect from the service object. If it still exists, it is guaranteed that disconnectFromServiceObject is called first.

See also acceptServiceObject(), connectToServiceObject(), and disconnectFromServiceObject().

[override virtual protected] void QIfAbstractFeature::componentComplete()

Reimplements: QQmlParserStatus::componentComplete().

Invoked automatically when used from QML. Calls startAutoDiscovery().

[virtual protected] void QIfAbstractFeature::connectToServiceObject(QIfServiceObject *serviceObject)

This method is expected to be implemented by any class subclassing QIfAbstractFeature.

The implementation should connect to the serviceObject, and set up all properties to reflect the state of the service object.

There is no previous service object connected, as this function call is always preceded by a call to disconnectFromServiceObject or clearServiceObject.

It is safe to assume that the serviceObject, has always been accepted through the acceptServiceObject method prior to being passed to this method.

The default implementation connects to the signals offered by QIfFeatureInterface and calls QIfFeatureInterface::initialize() afterwards.

When reimplementing please keep in mind to connect all signals before calling this function. e.g.

void SimpleFeature::connectToServiceObject(QIfServiceObject *serviceObject)
{
    SimpleFeatureBackendInterface *backend = backend(serviceObject);
    if (!backend)
        return;

    // connect your signals
    connect(backend, &SimpleFeatureBackendInterface::propertyChanged,
            this, &SimpleFeature::onPropertyChanged);

    // connects the base signals and call initialize()
    QIfAbstractFeature::connectToServiceObject(serviceObject);

    // Additional initialization functions can be added here
}

See also acceptServiceObject(), disconnectFromServiceObject(), and clearServiceObject().

[virtual protected] void QIfAbstractFeature::disconnectFromServiceObject(QIfServiceObject *serviceObject)

This method disconnects all connections to the serviceObject.

There is no need to reset internal variables to safe defaults. A call to this function is always followed by a call to connectToServiceObject or clearServiceObject.

The default implementation disconnects all signals from the serviceObject to this instance.

Most of the times you don't have to reimplement this method. A reimplementation is only needed if multiple interfaces have been connected before or special cleanup calls need to be done to the backend before disconnecting as well. If you need to reimplement this function, please make sure to use the interfaceName() method to retrieve the backend instance and not hardcode it to a particular interfaceName, as otherwise the disconnect calls don't work anymore with derived interfaces.

See also acceptServiceObject(), connectToServiceObject(), and clearServiceObject().

QIfAbstractFeature::Error QIfAbstractFeature::error() const

Returns the last error code.

See also setError() and QIfAbstractFeature::Error.

[protected] QString QIfAbstractFeature::errorText() const

Returns the current error code converted from QIfAbstractFeature::Error to QString

See also error.

[protected] QString QIfAbstractFeature::interfaceName() const

Returns the interface name this feature is implementing.

When the feature discovers a matching backend, this interface's name needs to be supported by the service object that the feature is connecting to.

See also acceptServiceObject.

[virtual protected slot] void QIfAbstractFeature::onErrorChanged(QIfAbstractFeature::Error error, const QString &message = QString())

Updates error and message from the backend.

Use this slot when you implement a new feature to report generic errors.

[protected] void QIfAbstractFeature::setError(QIfAbstractFeature::Error error, const QString &message = QString())

Sets error with the message.

Emits errorChanged() signal.

See also error() and QIfAbstractZonedFeature::Error.

[slot] QIfAbstractFeature::DiscoveryResult QIfAbstractFeature::startAutoDiscovery()

Performs an automatic discovery attempt.

The feature will try to locate a single service object implementing the required interface.

If no service object is found, the feature will stay invalid. If more than one service object is found, the first instance is used.

Either the type of the backend which was loaded or an error is returned.

If the discoveryMode is set to QIfAbstractFeature::NoAutoDiscovery this function will do nothing and return QIfAbstractFeature::NoResult.

See also discoveryMode() and Dynamic Backend System.