being_smart_about_ownership_2.cpp

//The header of Widget (the important bits for us)
class Widget {
public:
    void lock_widget_mutex();
    void unlock_widget_mutex();
    int  get_status() const;
    void trigger_event();
}

//A function which gives us pointers to these Widgets
Widget* get_widget();

//Now lets see how we use this library
//Lets assume we want to use the widget is it's status is 42
void use_widget() {
    auto widget_ptr = get_widget();
    if(widget_ptr->get_status() == 42)
        widget_ptr->trigger_event();
}

//That might be a valid way to use our pointer to a widget, here's another one:
void use_widget() {
    auto widget_ptr = get_widget();
    //Lock the widget since other threads might also be trying to use it
    widget_ptr->lock_widget_mutex();
    if(widget_ptr->get_status() == 42)
        widget_ptr->trigger_event();
    widget_ptr->unlock_widget_mutex();
}

// And here's another totally valid way to use it:
void use_widget() {
    auto widget_ptr = get_widget();
    //Maybe thge widget is unavailable so we should try getting it again
    while(widget_ptr == nullptr) {
        auto widget_ptr = get_widget();
    }
    if(widget_ptr->get_status() == 42)
        widget_ptr->trigger_event();
    //We no longer need the widget to lets free it
    free(widget_ptr);
}