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  1. #include <algorithm>
  2. #include <iostream>
  3. #include <functional>
  4. #include <vector>
  5. #include <set>
  6.  
  7. class Observer;
  8.  
  9. class IObserverNotifier
  10. {
  11. public:
  12.     virtual ~IObserverNotifier() = default;
  13.     virtual void UnRegister(Observer&) = 0;
  14. };
  15.  
  16. class Observer
  17. {
  18. public:
  19.     explicit Observer() = default;
  20.     virtual ~Observer() {
  21.         for (auto* abstractObserverNotifier : mAbstractObserverNotifiers)
  22.             abstractObserverNotifier->UnRegister(*this);   
  23.     }
  24.  
  25.     Observer(const Observer&) = delete;
  26.     Observer(Observer&&) = delete;
  27.     Observer& operator=(const Observer&) = delete;
  28.     Observer& operator=(Observer&&) = delete;
  29.  
  30.     void AddObserverNotifier(IObserverNotifier& observerNotifier)
  31.     {
  32.         mAbstractObserverNotifiers.insert(&observerNotifier);
  33.     }
  34.  
  35.     void RemoveObserverNotifier(IObserverNotifier& observerNotifier)
  36.     {
  37.         mAbstractObserverNotifiers.erase(&observerNotifier);
  38.     }
  39.  
  40. private:
  41.     std::set<IObserverNotifier*> mAbstractObserverNotifiers;
  42. };
  43.  
  44. template<typename ... Params>
  45. class ObserverNotifier : private IObserverNotifier
  46. {
  47. public:
  48.     ObserverNotifier() = default;
  49.     ~ObserverNotifier() {
  50.         for (const auto& p : mObserverCallbacks) {
  51.             p.first->RemoveObserverNotifier(*this);
  52.         }
  53.     }
  54.  
  55.     ObserverNotifier(const ObserverNotifier&) = delete;
  56.     ObserverNotifier(ObserverNotifier&&) = delete;
  57.  
  58.     ObserverNotifier& operator=(const ObserverNotifier&) = delete;
  59.     ObserverNotifier& operator=(ObserverNotifier&&) = delete;
  60.  
  61.     void Register(Observer& observer, std::function<void(Params...)> f) {
  62.         mObserverCallbacks.emplace_back(&observer, f);
  63.         observer.AddObserverNotifier(*this);
  64.     }
  65.  
  66.     void NotifyObservers(Params... args) const
  67.     {
  68.         for (const auto& p : mObserverCallbacks)
  69.         {
  70.             const auto& callback = p.second;
  71.  
  72.             callback(args...);
  73.         }
  74.     }
  75.  
  76. private:
  77.     void UnRegister(Observer& observer) override
  78.     {
  79.         mObserverCallbacks.erase(std::remove_if(mObserverCallbacks.begin(),
  80.                                                 mObserverCallbacks.end(),
  81.                                                 [&](const auto& p) { return p.first == &observer;}),
  82.                                  mObserverCallbacks.end());
  83.     }
  84.  
  85. private:
  86.     std::vector<std::pair<Observer*, std::function<void(Params...)>>> mObserverCallbacks;
  87. };
  88.  
  89.  
  90. class Sensor
  91. {
  92. public:
  93.     void ChangeTime() {
  94.         ++mTime;
  95.         mOnTimeChange.NotifyObservers(mTime);
  96.     }
  97.  
  98.     void ChangeTemperature(double delta) {
  99.         mTemperature += delta;
  100.         mOnTemperatureChange.NotifyObservers(mTemperature);
  101.     }
  102.  
  103.     void RegisterTimeChange(Observer& observer, std::function<void(double)> f) { mOnTimeChange.Register(observer, f); }
  104.     void RegisterTemperatureChange(Observer& observer, std::function<void(double)> f) { mOnTemperatureChange.Register(observer, f); }
  105.  
  106. private:
  107.     ObserverNotifier<int> mOnTimeChange;
  108.     ObserverNotifier<double> mOnTemperatureChange;
  109.     int mTime = 0;
  110.     double mTemperature = 0;
  111. };
  112.  
  113. class Ice : public Observer {
  114. public:
  115.  
  116.     void OnTimeChanged(int time) {
  117.         mVolume -= mLose;
  118.         mOnVolumeChange.NotifyObservers(mVolume);
  119.     }
  120.  
  121.     void OnTemperatureChanged(double t) {
  122.         if (t <= 0) {
  123.             mLose = 0;
  124.         } else if (t < 15) {
  125.             mLose = 5;
  126.         } else {
  127.             mLose = 21;
  128.         }
  129.     }
  130.  
  131.     void RegisterVolumeChange(Observer& observer, std::function<void(double)> f) { mOnVolumeChange.Register(observer, f); }
  132.  
  133.  
  134. private:
  135.     ObserverNotifier<double> mOnVolumeChange;
  136.     double mVolume = 42;
  137.     double mLose = 0;
  138. };
  139.  
  140. class MyObserver : public Observer {
  141. public:
  142.     static void OnTimeChange(int t) {
  143.         std::cout << "observer says time is " << t << std::endl;
  144.     }
  145.  
  146.     static void OnTemperatureChange(double temperature) {
  147.         std::cout << "observer says temperature is " << temperature << std::endl;
  148.     }
  149.  
  150.     static void OnIceChange(double volume) {
  151.         std::cout << "observer says Ice volume is " << volume << std::endl;
  152.     }
  153.  
  154. };
  155.  
  156. int main()
  157. {
  158.     Sensor sensor;
  159.     Ice ice;
  160.     MyObserver observer;
  161.  
  162.     sensor.RegisterTimeChange(observer, &MyObserver::OnTimeChange);
  163.     sensor.RegisterTemperatureChange(observer, &MyObserver::OnTemperatureChange);
  164.     ice.RegisterVolumeChange(observer, &MyObserver::OnIceChange);
  165.     sensor.RegisterTimeChange(ice, [&](int t){ice.OnTimeChanged(t);});
  166.     sensor.RegisterTemperatureChange(ice, [&](double t){ice.OnTemperatureChanged(t);});
  167.  
  168.     sensor.ChangeTemperature(0);
  169.     sensor.ChangeTime();
  170.     sensor.ChangeTemperature(10.3);
  171.     sensor.ChangeTime();
  172.     sensor.ChangeTime();
  173.     sensor.ChangeTemperature(42.1);
  174.     sensor.ChangeTime();
  175. }
  176.  
Success #stdin #stdout 0s 15256KB
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stdin
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Standard input is empty
stdout
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observer says temperature is 0
observer says time is 1
observer says Ice volume is 42
observer says temperature is 10.3
observer says time is 2
observer says Ice volume is 37
observer says time is 3
observer says Ice volume is 32
observer says temperature is 52.4
observer says time is 4
observer says Ice volume is 11
https://ideone.com/3OasIr
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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