// Purpose. Singleton design pattern lab.
//
// Problem. The application would like a single instance of globalObject
// to exist, and chooses to implement it as a global. Globals should
// always be discouraged. Additionally, any code that references the
// global object, has to first check if the pointer has been initialized,
// and initialize it if it has not.
//
// Assignment.
// o Replace the global variable globalObject with a private static data member.
// o Provide the pattern-specified accessor function.
// o Provide for initialization and init testing in the GlobalObject class.
// o All client code should now use the Singleton accessor function instead of
// referencing the globalObject variable.
// o Remove any client code dealing with globalObject initialization.
// o Guarantee that the GlobalObject class cannot be instantiated.

#include <iostream.h>


class GlobalObject {
public:
GlobalObject() : value_( 0 ) { }
int getValue() { return value_; }
void setValue( int val ) { value_ = val; }
private:
int value_;
};

GlobalObject* globalObject;


void foo( void ) {
if ( ! globalObject )
globalObject = new GlobalObject;
cout << "foo: globalObject's value is " << globalObject->getValue() << endl;
}

void bar( void ) {
if ( ! globalObject )
globalObject = new GlobalObject;
globalObject->setValue( 42 );
cout << "bar: globalObject's value is " << globalObject->getValue() << endl;
}


void main( void ) {
foo();
bar();
if ( ! globalObject )
globalObject = new GlobalObject;
cout << "main: globalObject's value is " << globalObject->getValue() << endl;
}

// foo: globalObject's value is 0
// bar: globalObject's value is 42
// main: globalObject's value is 42