/***************************************************************************************** ___// OBSERVER DESIGN PATTERN //___ Here is the implementation of observer design pattern in cpp. Basically observer is the class which has feature to register the class object which should be notified for an event. Desription: Subject: It is an interface class used to maintain polymorphic hierarchy. Observer: Class is responsible to pass an event to the registered classes. ObjectOne, ObjectTwo, ObjectThree: Event hander classes. SAGA@SAGA:~/Practice/design_patterns$ c++ observer_design_pattern.cpp -std=c++11 -g -o observ SAGA@SAGA:~/Practice/design_patterns$ ./observ ObjectOne :: How's you? ObjectTwo :: How's you? ObjectThree :: How's you? ObjectOne :: Are you Okay? ObjectTwo :: Are you Okay? ******************************************************************************************/ #include #include #include #include using namespace std; class Subject { public: virtual void notify(const char* str) {} virtual ~Subject() {} }; class Observer { private: vector _observer; public: Observer(int eventHandlers) { _observer.reserve(eventHandlers); } void registerObj(Subject* ob) { _observer.emplace_back(ob); } void unregisterObj(Subject* ob) { auto it = find(_observer.begin(), _observer.end(), ob); if(it != _observer. end()) { _observer.erase(it); } } void notify(const char* str) { for (auto &obj : _observer) { obj->notify(str); } } }; class ObjectOne: public Subject { public: virtual void notify(const char* str) { cout<<"ObjectOne :: "<