Classic Observer pattern was added.

Author: khajavi

Behavioural/Observer/Classic/C++/Main.cpp

@@ -0,0 +1,114 @@
+/*
+ * Adopted from http://www.cppblog.com/converse/archive/2006/08/05/10858.html
+ */
+
+#include <iostream>
+#include <list>
+#include <algorithm>
+using namespace std;
+
+typedef int STATE;
+
+class Observer;
+
+// Subject Interface (Observable)
+class Subject {
+public:
+	Subject()
+		:_subjectState( -1 ) {
+		}
+
+	void notify(); 
+
+	void attach( Observer* observer ) {
+		cout << "attach an Observer" << endl;
+		_listObserver.push_back( observer );
+	}
+
+	void detach( Observer* observer ) {
+		list<Observer*>::iterator iter;
+		iter = find( _listObserver.begin(), _listObserver.end(), observer );
+
+		if ( _listObserver.end() != iter ) {
+			_listObserver.erase( iter );
+		}
+		cout << "detach and Observer" << endl;
+	}
+
+	virtual void setState( STATE state ) {
+		cout << "setState by subject" << endl;
+		_subjectState = state;
+	}
+
+	virtual STATE getState() {
+		cout << "getState by subject" << endl;
+		return _subjectState;
+	}
+
+protected:
+	STATE _subjectState;
+	list<Observer*> _listObserver;
+};
+
+
+
+class Observer {
+public:
+	virtual void update( Subject* subject ) = 0;
+protected:
+	STATE _observerState;
+};
+
+class ConcreteSubject : public Subject {
+public:
+	virtual void setState( STATE state ) {
+		cout << "setState by ConcreteSubject" << endl;
+		_subjectState = state;
+	}
+
+	virtual STATE getState() {
+		cout << "getState by ConcreteSubject" << endl;
+		return _subjectState;
+	}
+};
+
+class ConcreteObserver : public Observer {
+public:
+	virtual void update( Subject* subject ) {
+		if ( NULL == subject )
+			return;
+		_observerState = subject->getState();
+		cout << "the ObserverState is " << _observerState << endl;
+	}
+};
+
+void Subject::notify() {
+	cout << "notify observer's state" << endl;
+
+	list<Observer*>::iterator iter1, iter2;
+	for ( iter1 = _listObserver.begin(), iter2 = _listObserver.end();
+			iter1 != iter2;
+			++iter1 ) {
+		(*iter1)->update( this );
+	}
+}
+
+int main() {
+
+	Observer* observer1 = new ConcreteObserver();
+	Observer* observer2 = new ConcreteObserver();
+
+	Subject* subject = new ConcreteSubject();
+
+	subject->attach( observer1 );
+	subject->attach( observer2 );
+
+	subject->setState( 4 );
+	subject->notify();
+
+	subject->detach( observer1 );
+	subject->setState( 10 );
+	subject->notify();
+
+	return 0;
+}