C++: I have this config class that I want to use between all my CPP files, how do I initialize it?

class Config
{
    public:

        static int OUTPUT_TO_FILE;
        static int NEED_TO_TRAIN;
        static int NO_FILE_TRAIN;
        static int NEED_TO_TEST;
}

Above is my header.h file (i followed: http://weblogs.asp.net/whaggard/archive/2004/11/05/252685.aspx)

and I want to be able to do things like Config.OUTPUT_TO_FILE = true or variable = Config.NO_FILE_TRAIN;

from any file that includes config.h

I have what I want to do is clear, Just want some variable shared throughout all my cpp files.

EDIT: I'm having trouble compiling:

In my make file, I added:

hPif : src/main.o src/fann_utils.o src/hashes.o src/config.o # 开发者_运维技巧added the config part
    g++ src/main.o src/fann_utils.o src/hashes.o src/config.o -lfann -L/usr/local/lib -o hPif

config.o : src/config.cpp src/config.h
    g++ -c src/config.cpp

.
.
.
main.o: src/main.cpp src/config.h src/main.h src/hashes.h
    g++ -c src/main.cpp

config.cpp:

#include "config.h"

int OUTPUT_TO_FILE = false;
.
.
.

config.h:

class Config
{
    public:

        static int OUTPUT_TO_FILE;
.
.
.

Trying to call by:

#include "config.h"
...

            Config::OUTPUT_TO_FILE = true;

Error I get:

Undefined Symbols:
  "Config::OUTPUT_TO_FILE", referenced from:
      _main in main.o
      _main in main.o

Header (Config.h):

#pragma once

class Config
{
public:
  static int OUTPUT_TO_FILE;
  static int NEED_TO_TRAIN;
  static int NO_FILE_TRAIN;
  static int NEED_TO_TEST;
};

Source (Config.cpp):

#include "Config.h"

int Config::OUTPUT_TO_FILE = 0;
int Config::NEED_TO_TRAIN = 0;
int Config::NO_FILE_TRAIN = 0;
int Config::NEED_TO_TEST = 0;

Usage (any.cpp):

#include "Config.h"

...
int variable = Config::OUTPUT_TO_FILE;
...

In one of your source files, add something like this:

int Config::OUTPUT_TO_FILE = 1;

Now, it will be initialized on program startup. Only do this in one source .cpp file, not in multiple.

Because the class only has statics, you should be able to access them in any file which includes this header, for example..

foo.cpp

#include "Config.h"

void bar()
{
  Config::NO_FILE_TRAIN = 0; // set this value for example
}

bar.cpp

#include "Config.h"

void foo()
{
  Config::NEED_TO_TRAIN = 1; // set this value for example
}

Remember you must have an implementation file that is also compiled which actually defines the statics, i.e.

Config.cpp

int Config::OUTPUT_TO_FILE = 0; // initial value
:  //etc.

You might want to implement your Config class as a singleton.

Oh, and if you want to set OUTPUT_TO_FILE = true, you'd be better off declaring OUTPUT_TO_FILE as bool...