static members

[Lem]

The following code compiles fine, however when I try to execute it, I get
this:
main.obj : error LNK2001: unresolved external symbol "private: static int
Class::dI" (?dI@Class@@0HA )
It works fine when I do not use dI.

#include<iostre am.h>

class Class{
static int dI;
public:
int I;
static void init();
};

void Class::init(){
if(!(dI)){
dI = 100;
}
}

void main(){
Class a;
Class::init();
a.I = 2;
cout<<a.I;
}

Thanks in advance,
Lem

[Rolf Magnus]

Re: static members

Lem wrote:
[color=blue]
> The following code compiles fine, however when I try to execute it, I
> get this:
> main.obj : error LNK2001: unresolved external symbol "private: static
> int Class::dI" (?dI@Class@@0HA )
> It works fine when I do not use dI.[/color]
[color=blue]
> #include<iostre am.h>[/color]

This header is non-standard. Use <iostream> instead.
[color=blue]
> class Class{
> static int dI;
> public:
> int I;
> static void init();
> };[/color]

The problem is that you declare dI, but you don't define it anywhere. A
non-static member variable is instantiated when an object of the class
is created, but a static member must be defined explicitly. So add:

int Class:dI;
[color=blue]
> void Class::init(){
> if(!(dI)){
> dI = 100;
> }
> }
>
> void main(){[/color]

main() must return int.
[color=blue]
> Class a;
> Class::init();
> a.I = 2;
> cout<<a.I;[/color]

If you use <iostream>, you need to change that into:

std::cout<<a.I;
[color=blue]
> }
>
> Thanks in advance,
> Lem[/color]

--
"Ziel des Spieles ist es, Länder zu überfallen, Kontinente und die
Welt zu erobern, sowie Gegner zu schlagen." -- Risiko 1976
"Ziel des Spieles ist es, Länder und Kontinente von Besatzungsarmee n
zu befreien und in die Unabhängigkeit zu führen." -- Risiko 1990

[Nick Hounsome]

Re: static members


"Lem" <hjlem@pacific. net.sg> wrote in message
news:c1sgs5$phc $2@nobel2.pacif ic.net.sg...[color=blue]
> The following code compiles fine, however when I try to execute it, I get
> this:
> main.obj : error LNK2001: unresolved external symbol "private: static int
> Class::dI" (?dI@Class@@0HA )
> It works fine when I do not use dI.
>
> #include<iostre am.h>
>
> class Class{
> static int dI;
> public:
> int I;
> static void init();
> };
>
> void Class::init(){
> if(!(dI)){
> dI = 100;
> }
> }
>
> void main(){
> Class a;
> Class::init();
> a.I = 2;
> cout<<a.I;
> }
>
> Thanks in advance,
> Lem[/color]

int Class::dI = 100;

and you don't need the init function either!

(and you probably wanted and endl in the output.)