QIfZonedFeatureInterface Class

Detailed Description

Implementing QIfZonedFeatureInterface follows the same pattern as described in QIfFeatureInterface, but to support zones some additional functions need to be implemented: all setters and signals which are zoned need to be adapted like described below.

Providing Available Zones

Before making any further calls to the backend, The zoned feature will query the list of available zones. Zones are string keys and can be anything defined by the backend developer. In this case we have two zones: "Left" and "Right":

QStringList Backend::availableZones() const {
    QStringList zones;
    zones << "Left";
    zones << "Right";
    return zones;
}

Signal Definition

A zoned signal or a change signal for a zoned property needs to provide the zone as the second parameter. Here an example for a zoned signal:

void fanSpeedLevelChanged(int value, const QString &zone);

Similar to implementing a QIfFeatureInterface, the backend needs to emit all property change signals with the initial values in the initialize() function. In a zoned backend, the implementation has to emit all supported property signals, passing the zone as a parameter. The zone parameter can be omitted if the property is unzoned.

void Backend::initialize() {
    emit fanSpeedLevelChanged(2, "Left");
    emit fanSpeedLevelChanged(2, "Right");
    emit steeringWheelHeaterChanged(0); // Generic, no zone specified
    emit initializationDone();
}

Setter implementation

A setter for a zoned property takes the zone as the second parameter after the property value. Validating the requested zone is the responsibility of the backend implementation and in case an unsupported zone is passed, a QIfAbstractFeature::InvalidZone error should be reported.

In the example, the fanSpeedLevel property is zoned. If zone is valid, the actual fan speed level is adjusted and afterwards the change signal is emitted to indicate the change to the feature.

void Backend::setFanSpeedLevel(int value, const QString &zone) {
    if (!m_fanSpeedZones.contains(zone)) {
        emit errorChanged(QIfAbstractFeature::InvalidZone);
    } else {
        // Set specified zone fan to value
        ...
        emit fanSpeedLevelChanged(value, zone);
    }
}