Language: C++ (QT)
class Foo :public QObject{
Q_OBJECT
public:
	Foo(int i);
	void decrement(int i);
	void increment(int i);
signal:
	void changeVal(int i, Qstring changeType);
private:
	int x;
}
 
foo.cpp
	void Foo::decrement(int i){
		x =x+i;
		emit changeVal(x,"dec");
	}
	void Foo:increment(int i) {
		x = x-i;
		emit changeVal(x,"inc");
	}
 
 
class FooDisplay:public QObject{
Q_OBJECT
public:
	FooDisplay();
slots:
	void showChange(int i, QString chageType);
private:
	int x;
 
FooDisplay.cpp
...
void FooDisplay::showChange(int i, QString changeType) {
	if (changeType=="inc")
		cout << "Incrmenting x "<<i<<"\n";
	if (changeType=="dec")
		cout << "Decrementing x "<<i<<"\n";
}
...

Language: C++ (QT)
Foo f;
FooDisplay fd;
connect(&f,SIGNAL(changeVal(int,QString)),&fb,SLOT(showChange(int,QString);
f.incrment(10);
f.decremet(5);

Language: C++ (QT)
virtual void showChange(int i,QString outType)=0;

Language: C++ (QT)
class OutConsole:public FooDisplay {
public:
	OutConsole() {}
	void showChange(int i, QSTring changeType) {
	QTextStream cout(stdout); //send it to console with this concrete class
		if (changeType=="inc")
		cout << "Incrmenting x "<<i<<"\n";
		if (changeType=="dec")
		cout << "Decrementing x "<<i<<"\n";
	}
}
 
class OutFile:public FooDisplay {
	void showChange(int i, QSTring changeType) {
		QFile f("random.txt")
		f.open(QFile::writeonly);
		QTextStream fout(&f); //send it to file with this concrete class
 
		if (changeType=="inc")
		fout << "Incrmenting x "<<i<<"\n";
		if (changeType=="dec")
		fout << "Decrementing x "<<i<<"\n";
		f.close();
	}
 
}

Language: C++ (QT)
FooDisplay* foodistCon = new OutConsole(); // stratergy Console
FooDisplay* foodistFile = new OutFile(); // stratergy File
Foo f;
connnect(&f,SIGNAL(changeValue(int,QString),foodistCon(int,Qstring));
connnect(&f,SIGNAL(changeValue(int,QString),foodistFile(int,Qstring));