/**
     * Sets a common callback function for all members.
     */
    void set_callback_on_value_change(const std::function<void(twidget&)>& func)
    {
        const std::function<void(twidget&)> callback = [&func](tselectable_* widget)->void {
            if(widget->get_value_bool()) {
                func(*dynamic_cast<twidget*>(widget));
            }
        };

        for(auto& member : members())
        {
            member.first->set_callback_state_change(callback(member.first));
        }
    }