Observable Design

observables.hh

typedef std::function<std::function<void()>(Observer<T>)> SubscriberFunction<T>;

interface Subscription<T> {
  Subscription<T>(Observer<T>, SubscriberFunction<T>);
  void unsubscribe();
}

interface Observer<T> {
  void start(Subscription<T>);
  void next(const T&);
  void error(const std::exception&);
  void complete();
}

interface Observable<T> {
  Observable<T>(SubscriberFunction<T>);
  Subscription &subscribe(Observer<T>);
  Subscription &subscribe(std::function<void(const T&));
}

interface Subject<T> extends Observable<T> {
  Subject<T>();
  void next(const T&);
  void error(const std::exception&);
  void complete();
}