Detailed Description

Using C++ models is useful for exposing existing C++ data models or other complex datasets to QML. Creating a model in C++ is the only way to have a non-readonly model: The ones defined in QML cannot be modified at runtime.

To create your own model, first declare a struct that describes the data model. Its public fields become the model roles. The struct must be equality-comparable.

struct AlarmData
{
    AlarmData()
        : seconds(0)
        , running(false)
    {}

    AlarmData(int argSeconds, bool argRunning)
        : seconds(argSeconds)
        , running(argRunning)
    {}

    int seconds;
    bool running;
};

inline bool operator==(const AlarmData &lhs, const AlarmData &rhs)
{
    return lhs.seconds == rhs.seconds && lhs.running == rhs.running;
}

Alternatively, the template argument can be a simple type supported by Qt Quick Ultralite (for example, int or Qul::qreal).

Then, declare a struct that derives directly from Qul::ListModel.

struct AlarmModel : Qul::ListModel<AlarmData>
{
private:
    std::vector<AlarmData, Qul::PlatformInterface::Allocator<AlarmData> > m_data;

public:
    // Implement the ListModel interface
    int count() const QUL_DECL_OVERRIDE { return m_data.size(); }
    AlarmData data(int index) const QUL_DECL_OVERRIDE { return m_data[index]; }

This struct may contain additional functions that the QML application can use to interact with the model:

void togglePause(int index)
{
    m_data[index].running = !m_data[index].running;
    dataChanged(index);
}

The modelReset and dataChanged signals are used to trigger a refresh of a view.

The modelReset signal must be emitted whenever number of elements of the model changes after it's instantiation by a view.

The dataChanged signal must be emitted whenever existing element of the model is modified.

Dynamic strings

Passing strings form C++ to QML has some implications on how glyphs are generated by the fontcompiler. It's possible that some characters will not be rendered in the QML by default. For more detailed description see Rendering dynamic strings in QML.