SDSU CS 596 OODP
Correction on Copy Constructors

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San Diego State University -- This page last updated Oct. 28, 1995
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Copying - Default Copy Constructor 

#include <iostream.h>

class OK {
	public:
		int size;
		OK( int initialSize = 10 );
		~OK() {  cout << "Kill OK: " << size << endl; };
};

OK :: OK( int initialSize ) {
	size = initialSize; 
	cout << "New OK: " << initialSize << endl;
};

class Trouble {
	public:
		int Location;
		OK test;
		Trouble( int StartValue = 5 );

};

Trouble :: Trouble(  int StartValue )	{
	Location =StartValue ; test.size = 20;
};

void main() {
	Trouble NotMe;
	Trouble ThisIsFine = NotMe;
};
Output 
New OK: 10
Kill OK: 20
Kill OK: 20

Copying - Implicit Call to Copy Constructor 

#include <iostream.h>

class OK {
	public:
		int* size;
		OK( int initialSize = 10 );
		OK( const OK& Copy );
		~OK() {delete size; cout << "Kill OK " << *size << endl; };
};

OK :: OK( int initialSize ) {
	size = new int( initialSize ); 
	cout << "New OK: " << initialSize << endl; };

OK :: OK( const OK& Copy ) {
	size = new int( *(Copy.size) ); 
	cout << "New Copy OK: " << *size << endl; };

class Trouble {
	public:
		int Location;
		OK test;
		Trouble( int StartValue = 5 );
};

Trouble :: Trouble(  int StartValue )	{
	Location =StartValue ; *(test.size) = 20;};

void main() {
	Trouble NotYet;
	Trouble ThisIsFine = NotYet;};
Output 
New OK: 10	Kill OK 20
New Copy OK: 10	Kill OK 20
Copying - Copy Constructor in Copy Constructor 
class OK {
	public:
		int* size;
		OK( int initialSize = 10 );
		OK( const OK& Copy );
		~OK() {delete size; cout << "Kill OK:" << *size << endl; }; };

// See previous page for OK constructors

class Trouble {
	public:
		int* Location;
		OK test;
		Trouble( int StartValue = 5 );
		Trouble( const Trouble& Copy ); };

Trouble :: Trouble(  int StartValue )	{
	Location =  new int(StartValue) ; *(test.size) = 20;  };

Trouble :: Trouble(  const Trouble& Copy )	{
	Location =  new int( *(Copy.Location) ) ;  };

void main() {
	Trouble Now;
	Trouble ThisIsIt = Now; };
Output 
New OK: 10	Kill OK 10
New OK: 10	Kill OK 20
Solution 
class OK {
	public:
		int* size;
		OK( int initialSize = 10 );
		OK( const OK& Copy );
		~OK() {delete size; cout << "Kill OK:" << *size << endl; }; };

// See previous page for OK constructors


class Trouble {
	public:
		int* Location;
		OK test;
		Trouble( int StartValue = 5 );
		Trouble( const Trouble& Copy ); };

Trouble :: Trouble(  int StartValue )	{
	Location =  new int(StartValue) ; *(test.size) = 20;  };

Trouble :: Trouble(  const Trouble& Copy )	: test( Copy.test ) {
	Location =  new int( *(Copy.Location) ) ;  };

void main() {
	Trouble Now;
	Trouble ThisIsIt = Now; };
Output 
New OK: 10	Kill OK 20
New Copy OK: 20	Kill OK 20