question about static variables

[sieg1974]

Hi,

I have this following class, but when I compile it, gcc shows a error
message "undefined reference to `Animal::theNumberOfAnimals`".
I know this must be very easy to fix, but for a newnie like me it's
not :-P

Thanks in advance,

Andre

class Animal
{
private:
char theName[ 128 ];
static int theNumberOfAnimals;

public:
Animal()
{
theNumberOfAnimals++;
};

Animal( char * name )
{
strcpy( theName, name );
theNumberOfAnimals++;
};

~Animal(){};
};

[John Carson]

"sieg1974" <si******@yahoo.com> wrote in message
news:89**************************@posting.google.c om

Hi,

I have this following class, but when I compile it, gcc shows a error
message "undefined reference to `Animal::theNumberOfAnimals`".
I know this must be very easy to fix, but for a newnie like me it's
not :-P

Thanks in advance,

Andre

class Animal
{
private:
char theName[ 128 ];
static int theNumberOfAnimals;

public:
Animal()
{
theNumberOfAnimals++;
};

Animal( char * name )
{
strcpy( theName, name );
theNumberOfAnimals++;
};

~Animal(){};
};

static variables are like member functions in that you declare them in the
class declaration and then define them outside it. Typically, the definition
is done in a .cpp file rather than a header file since (like a function
definition) it must be done only once. Just add:

int Animal::theNumberOfAnimals;

in a .cpp file (note that you must NOT use the static keyword in the
definition).
--
John Carson
1. To reply to email address, remove donald
2. Don't reply to email address (post here instead)

[Dan Bloomquist]

sieg1974 wrote:

class Animal
{
private:
static int theNumberOfAnimals;
};

you need to define/( and should initailize) static members. In the
appropriate cpp file:

int Animal::theNumberOfAnimals= 0;

And it works even if private!

Best, Dan.

--
http://lakeweb.net
http://ReserveAnalyst.com
No EXTRA stuff for email.

[The King of Pots and Pans]

On Wed, 21 Apr 2004 at 03:54 GMT, sieg1974 spoke:

Animal()
{
theNumberOfAnimals++;
};

Animal( char * name )
{
strcpy( theName, name );
theNumberOfAnimals++;
};

~Animal(){};

What's with the semi-colons after the last curly brace of each
function?

--
The King of Pots and Pans

[David Harmon]

On Wed, 21 Apr 2004 07:11:38 GMT in comp.lang.c++, The King of Pots and
Pans <Ki**@ask.for.email.invalid> wrote,

What's with the semi-colons after the last curly brace of each
function?

It's a handy place to store spares, so if you forget a semicolon
elsewhere, as often happens, you can just grab one from nearby
and place it where needed. Sometimes you will see three or four
semicolons after a function just for that reason.

[Rakesh Kumar]

David Harmon wrote:

On Wed, 21 Apr 2004 07:11:38 GMT in comp.lang.c++, The King of Pots and
Pans <Ki**@ask.for.email.invalid> wrote,

What's with the semi-colons after the last curly brace of each
function?

It's a handy place to store spares, so if you forget a semicolon
elsewhere, as often happens, you can just grab one from nearby
and place it where needed.

Is that a suggested style of writing it or is it that only novices
use it. IMHO, it degrades readability of the code.

--
Rakesh Kumar
** Remove nospamplz from my email address for my real email **

[David Harmon]

On Wed, 21 Apr 2004 15:39:11 -0700 in comp.lang.c++, Rakesh Kumar
<dr******************@yahoo.com> wrote,

David Harmon wrote:

On Wed, 21 Apr 2004 07:11:38 GMT in comp.lang.c++, The King of Pots and
Pans <Ki**@ask.for.email.invalid> wrote,

What's with the semi-colons after the last curly brace of each
function?

It's a handy place to store spares, so if you forget a semicolon
elsewhere, as often happens, you can just grab one from nearby
and place it where needed.

Is that a suggested style of writing it or is it that only novices
use it. IMHO, it degrades readability of the code.

It's a joke. You don't need to store spare semicolons.