ObserverPattern.h

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2014 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once
#include <functional>
#include <set>
#include <string>
 
class Observable;
 
class Observer {
public:
  virtual ~Observer(){};
  virtual void update() = 0;
};
 
class Observable {
  std::set<Observer *> m_observers;
 
public:
  void attach(Observer *listener) { m_observers.insert(listener); };
  void detach(Observer *listener) { m_observers.erase(listener); };
  void notify() {
    for (auto &listener : m_observers) {
      listener->update();
    }
  };
};
 
class VoidObserver : public Observer {
public:
  VoidObserver() : m_slot(nullptr){};
  ~VoidObserver(){};
  void setSlot(const std::function<void()> &func) { m_slot = func; };
  void update() override { m_slot(); };
 
private:
  std::function<void()> m_slot;
};