static data member

what is meaning of this? (MS VC++ .NET)
----------------------
Linking...
machine.obj : error LNK2001: unresolved external symbol "private: static class std::vector<str uct GessoidMachine: :Resolution,cla ss
std::allocator< struct GessoidMachine: :Resolution> > GessoidMachine: :Machine::resol ution"
(?resolution@Ma chine@GessoidMa chine@@0V?$vect or@UResolution@ GessoidMachine@ @V?$allocator@U Resolution@Gess oidMachine@@@st d@@@std@@A)
machine.obj : error LNK2001: unresolved external symbol "private: static struct SDL_Surface * GessoidMachine: :Machine::scree n"
(?screen@Machin e@GessoidMachin e@@0PAUSDL_Surf ace@@A)
machine.obj : error LNK2001: unresolved external symbol "private: static int GessoidMachine: :Machine::resol ution_index"
(?resolution_in dex@Machine@Ges soidMachine@@0H A)
..\Debug/main.exe : fatal error LNK1120: 3 unresolved externals
----------------------

The error is in this code: (All member functions & data are static because I want only one instance of "Machine" in my project and I
want access in any data member without this->
----------------------
class Machine {
public:
static member1(arg1, arg2);
static member2();
.......
private:
// handle all resolutions supported from system
static vector <Resolution> resolution;
static int resolution_inde x;
static SDL_Surface *screen;
};
----------------------

[John Carson]

"<- Chameleon ->" <ch******@hotma il.NOSPAM.com> wrote in message
news:bv******** **@nic.grnet.gr

what is meaning of this? (MS VC++ .NET)
----------------------
Linking...
machine.obj : error LNK2001: unresolved external symbol "private:
static class std::vector<str uct GessoidMachine: :Resolution,cla ss
std::allocator< struct GessoidMachine: :Resolution> >
GessoidMachine: :Machine::resol ution"
(?resolution@Ma chine@GessoidMa chine@@0V?$vect or@UResolution@ GessoidMachine@ @
V?$allocator@UR esolution@Gesso idMachine@@@std @@@std@@A) machine.obj : error LNK2001: unresolved external symbol "private:
static struct SDL_Surface * GessoidMachine: :Machine::scree n"
(?screen@Machin e@GessoidMachin e@@0PAUSDL_Surf ace@@A)
machine.obj : error LNK2001: unresolved external symbol "private:
static int GessoidMachine: :Machine::resol ution_index"
(?resolution_in dex@Machine@Ges soidMachine@@0H A) .\Debug/main.exe :
fatal error LNK1120: 3 unresolved externals
----------------------

The error is in this code: (All member functions & data are static
because I want only one instance of "Machine" in my project and I
want access in any data member without this->
----------------------
class Machine {
public:
static member1(arg1, arg2);
static member2();
.......
private:
// handle all resolutions supported from system
static vector <Resolution> resolution;
static int resolution_inde x;
static SDL_Surface *screen;
};
----------------------

static data members are like member functions: you declare them in the
header file and then define them in the .cpp file. Basically, storage is
allocated for ordinary data members when you define an object of the class.
But static data members are independent of any class object and hence you
need to define them separately in order for storage to be allocated for
them.

Thus your .cpp file needs to contain:

vector <Resolution> Machine::resolu tion;
int Machine::resolu tion_index;
SDL_Surface *Machine::scree n;

Note that you must omit the static keyword in these definitions.
--

John Carson
1. To reply to email address, remove donald
2. Don't reply to email address (post here instead)

Aaaaaaaaa!!!!!!

How much idiot I am?