Je lis toujours Head First Design Patterns. J'en suis au Capitre 2 à la page 37 où l'on parle du Observer. Ce coup-ci j'ai ajouté un peu plus de commentaires dans le code source de mon Observer en C++... Ça ne fait jamais de mal. Cela dit, avec le bouquin ça devrait aller.
Ce que j'ai retenu
Plus tard, je vais mettre ici mes notes à propos du Design Patterns en question. Là il n'y a rien car j'ai collé le code et zou, je suis passé à autre chose.
Le code
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/*See Chapter II, page 37 Subject - Interface -----------------> Observer - Interface ------------------- --------------------- RegisterObserver Update RemoveObserver NotifyObservers ^ | ^ | | | | | Concrete Subject <----------------- Concrete Observer ---------------- ------------------ RegisterObserver Update RemoveObserver ... NotifyObservers ...*/#ifdef _MSC_VER #define _CRTDBG_MAP_ALLOC #include <crtdbg.h>#endif#include <iostream>#include <memory>#include <list>#include <vector>#include <numeric> // accumulateusing namespace std;// ----------------------------------------------------------------------------class ObserverInterface{public: virtual void Update(double humidity, double temp, double pressure) = 0; // See Strategy source code for comments virtual ~ObserverInterface() = 0 {};};class SubjectInterface{public: virtual void RegisterObserver(ObserverInterface *o) = 0; virtual void RemoveObserver(ObserverInterface *o) = 0; virtual ~SubjectInterface() = 0 {};private: virtual void NotifyObservers(void) const = 0;};class DisplayElementInterface{public: virtual void Display(void) const = 0; virtual ~DisplayElementInterface() = 0 {}};// ----------------------------------------------------------------------------// Tracks the data coming from the weather station and updates the displays// WeatherData is the concrete subjectclass WeatherData : public SubjectInterface {private: double mHumidity; double mTemperature; double mPressure; list<ObserverInterface*> mObservers;public: void RegisterObserver(ObserverInterface *o) { mObservers.push_back(o); } void RemoveObserver(ObserverInterface *o) { mObservers.remove(o); } void NotifyObservers(void) const { for (auto o : mObservers){ o->Update(mHumidity, mTemperature, mPressure); } } // In real life, it is supposed to be called by the weather station directly void MeasurementChanged(void){ NotifyObservers(); } // Helper-Fake function. // Everything looks like, data are updated by the weather station and then MeasurementChanged() gets called by the weather station void SetMeasurements(double Humidity, double Temperature, double Pressure){ mHumidity = Humidity; mTemperature = Temperature; mPressure = Pressure; MeasurementChanged(); }};// ----------------------------------------------------------------------------// Shows to the users the current weather conditions// A concrete Observer and a concrete Displayclass CurrentConditionsDisplay : public ObserverInterface, public DisplayElementInterface{private: double mHumidity; double mTemperature; double mPressure; SubjectInterface& mWeatherData; // Keep a ref to the Subject just in case. Not used here howeverpublic: CurrentConditionsDisplay(SubjectInterface& weatherData) : mWeatherData(weatherData) { mWeatherData.RegisterObserver(this); } // Implementation from the ObserverInterface void Update(double Humidity, double Temperature, double Pressure) { mHumidity = Humidity; mTemperature = Temperature; mPressure = Pressure; Display(); } // Implementation from the DisplayElementInterface void Display(void) const { cout << "Current Conditions Display :" << endl; cout << "\tHumidity : " << mHumidity << endl; cout << "\tTemperature : " << mTemperature << endl; cout << "\tPressure : " << mPressure << endl; cout << endl; }};// ----------------------------------------------------------------------------class AveragedConditionsDisplay : public ObserverInterface, public DisplayElementInterface{private: vector<double> mHumidity; vector<double> mTemperature; vector<double> mPressure; SubjectInterface& mWeatherData;public: AveragedConditionsDisplay(SubjectInterface& weatherData) : mWeatherData(weatherData){ mWeatherData.RegisterObserver(this); } void Update(double Humidity, double Temperature, double Pressure) { mHumidity.push_back(Humidity); mTemperature.push_back(Temperature); mPressure.push_back(Pressure); Display(); } void Display(void) const { cout << "Averaged Display :" << endl; cout << "\tAverage humidity : " << accumulate(mHumidity.begin(), mHumidity.end(),0.0)/mHumidity.size() << endl; cout << "\tAverage temperature : " << accumulate(mTemperature.begin(), mTemperature.end(), 0.0) / mTemperature.size() << endl; cout << "\tAverage pressure : " << accumulate(mPressure.begin(), mPressure.end(), 0.0) / mPressure.size() << endl; cout << endl; }};// ----------------------------------------------------------------------------static void Test(void){ WeatherData MyWeatherDataObject; CurrentConditionsDisplay CurrentDisplay(MyWeatherDataObject); AveragedConditionsDisplay StatisticDisplay(MyWeatherDataObject); // Simulate new weather measurements MyWeatherDataObject.SetMeasurements(80, 22, 1013); MyWeatherDataObject.SetMeasurements(85, 25, 1023); MyWeatherDataObject.SetMeasurements(90, 26, 1020); MyWeatherDataObject.SetMeasurements(85, 25, 1025); MyWeatherDataObject.RemoveObserver(&StatisticDisplay); cout << "Now we have one display." << endl << endl; MyWeatherDataObject.SetMeasurements(100, 40, 1000);}// ----------------------------------------------------------------------------int main(){#ifdef _MSC_VER _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);#endif Test(); // Putting all code in Test that way, allow to check memory leaks#ifdef _MSC_VER _CrtMemDumpAllObjectsSince(NULL); // Begins the dump from the start of program execution _CrtDumpMemoryLeaks();#endif cout << endl << "Strike ENTER to exit : "; cin.ignore((numeric_limits<streamsize>::max)(), '\n');} |
Prochaine étape ? Chapitre III et le Decorator pattern
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