Observable Library

Copyright (C) 2016-present David Capello

Library to use the observer pattern in C++11 programs with observable/observer classes or signals/slots.

Features

• Generate an observable notification/signal from multiple threads
• Add/remove observers/slots from multiple threads
• Erase/disconnect an observer/slot from the same observable notification/signal
• Reconnect an observer in the same notification

Observable

An observable Widget:

#include "obs.h"

class WidgetObserver {
public:
  virtual ~WidgetObserver() = 0;
  virtual void onClick() { }
};

class Widget : public obs::observable<WidgetObserver> {
public:
  void processClick() {
    notify_observers(&WidgetObserver::onClick);
  }
};

An example

#include "obs.h"

class ObserveClick : public WidgetObserver {
public:
  void onClick() override {
    // Do something...
  }
};

...
ObserveClick observer;
Widget button;
button.add_observer(&observer);

Signal

#include "obs.h"

int main() {
  obs::signal<void (int, int)> sig;
  sig.connect([](int x, int y){ ... });
  sig(1, 2); // Generate signal
}

Safe vs Fast

There are two variants of signals and observers:

• obs::safe_signal vs obs::fast_signal
• obs::safe_observers vs obs::fast_observers

The only difference between both is that the "fast" version uses obs::fast_list instead of obs::safe_list, where the former keeps track of slots with a std::vector and the later one is a thread-safe version list to connect/disconnect slots from different threads.

By default and for backward compatibility, obs::signal and obs::observers use the safe version, but you can enable the OBSERVABLE_FAST_LIST option to switch from obs::safe_list to obs::fast_list which is recommended for most cases (e.g. you don't need to do strange connections/disconnections as in tests).