singletonpattern.cpp

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//: C10:SingletonPattern.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
#include <iostream>
using namespace std;

class Singleton {
  static Singleton s;
  int i;
  Singleton(int x) : i(x) { }
  Singleton& operator=(Singleton&);  // Disallowed
  Singleton(const Singleton&);       // Disallowed
public:
  static Singleton& instance() { return s; }
  int getValue() { return i; }
  void setValue(int x) { i = x; }
};

Singleton Singleton::s(47);

int main() {
  Singleton& s = Singleton::instance();
  cout << s.getValue() << endl;
  Singleton& s2 = Singleton::instance();
  s2.setValue(9);
  cout << s.getValue() << endl;
} ///:~