QIfFeatureInterface Class

Detailed Description

To implement a backend for a specific feature, you need to derive from this class. There's a one-to-one mapping between a specialized feature API and its corresponding feature interface class.

The feature interface class specifies which functions and signals need to be implemented by a backend to work with a specific feature.

This base class contains the initialization logic and the generic error handling, which is common between all interfaces.

A feature interface for coffee machine could look like this:

class CoffeMachineInterface : public QIfFeatureInterface
{
    void setTargetTemperature(int targetTemperature) = 0;
    ...

signals:
    void currentTemperatureChanged(int currentTemperature);
    void targetTemperatureChanged(int targetTemperature);
    ...
}

A backend implementation providing the actual functionality needs to implement all pure-virtual functions and the logic to provide property updates and their initial state. Once the feature knows which backend implementation needs to be used, it will request the initial state of all properties by calling the initialize() function. The implementation needs to emit the changed signals with the initial values and once it is done, emit the initializationDone signal.

In the coffee machine example the implementation could look like this:

class CoffeMachineImplementation : public CoffeMachineInterface
{
    void initialize()
    {
        emit currentTemperature(0);
        emit targetTemperature(0);
        emit initializationDone();
    }

    void setTargetTemperature(int targetTemperature)
    {
        if (m_targetTemperature == targetTemperature)
            return;

        // adjust the heating element to the new target temperature
        emit targetTemperatureChanged(targetTemperature)
    }
}

The implementation for setTargetTemperature() controls the internal heating element and once that is done, the change signal is emitted to inform the feature about the new state of the property.