C++ macro integers and object definitions

Question

I lack of experience with C++ and I am trying to create a Settings file to put all my definitions and global variables there, so my project's classes can access those the values from there. The Settings.h file could look like this:

#ifndef SETTINGS_H_
#define SETTINGS_H_

#define COLOR_BLUE = Vec3b(255, 0, 0);
#define COLOR_GREEN = Vec3b(0, 255, 0);
#define NOT_SET = 0;
#define IN_PROCESS = 1;
#define SET = 2;
#define FGD_PX = 255;
#define BGD_PX = 127;

#include <cv.h>
using namespace cv;

class Settings {
};
#endif /* SETTINGS_H_ */

The idea is to access the variables without instantiate the class but just including it.

Is there any beautiful way to do this?

cheers,

Don't put `using namespace ...` directives in header files. Never. Under no circumstances. — Oswald, Nov 17 '13 at 21:37
`#define` 's have global scope and are not type safe. best to use `static const` — corn3lius, Nov 17 '13 at 21:40
why shouldn't I use namespace in header files, [Oswald](http://stackoverflow.com/users/534124/oswald)? — marcelosalloum, Nov 17 '13 at 21:58
[“using namespace” in c++ headers](http://stackoverflow.com/a/5849668/2176127) — , Nov 17 '13 at 22:36

score 2 · Accepted Answer · 2013-11-17T21:59:51.163

2

#include <cv.h>
using namespace cv;

#ifndef SETTINGS_H_
#define SETTINGS_H_

#define COLOR_BLUE Vec3b(255, 0, 0)
#define COLOR_GREEN Vec3b(0, 255, 0)
#define NOT_SET 0
#define IN_PROCESS 1
#define SET 2
#define FGD_PX 255
#define BGD_PX 127

class Settings {
public:
   static int var1;
   static float var2;
   static short var3;
};

// initialization
int Settings::var1 = SET;
float Settings::var2 = 3.14;
short Settings::var3 = BGD_PX;

#endif /* SETTINGS_H_ */

Usage:

int tmp = Settings::var1;

edited Nov 17 '13 at 21:59

answered Nov 17 '13 at 21:39

2

Of course you don't want those static definitions in the header. – chris Nov 17 '13 at 21:41
2

As of c++11 you can initialize them directly in the declaration. – Nov 17 '13 at 21:44
1

The `using namespace` declaration should **never** be in a header file. – Zac Howland Nov 17 '13 at 21:59

score 2 · Answer 2 · answered Nov 17 '13 at 21:52

2

Constants either go in enums, or as static consts. Manifest constants generally are reserved for compiler type options:

#ifndef SETTINGS_H_
#define SETTINGS_H_

class Settings {
public:
   static const vec3b color_blue;
   static const vec3b color_green;
   enum statics {
         NOT_SET = 0,
         IN_PROCESS = 1,
         SET = 2,
         FGD_PX = 255,
         BGD_PX = 127
   };

};

vec3b Settings::color_blue(255, 0, 0);
vec3b Settings::color_green(0, 255, 0);

#include <cv.h>

#endif

answered Nov 17 '13 at 21:52

Glenn Teitelbaum

10,108
3
36
80

And once again: As of c++11 you can initialize member variables in the declaration. – Nov 17 '13 at 21:55
@user2176127 I was so excited to remove all the manifest constants, I didnt want to have to worry about portability – Glenn Teitelbaum Nov 17 '13 at 23:40

score 0 · Answer 3 · answered Nov 17 '13 at 21:42

0

You shouldn't have equals signs or semicolons with #defines. What do you plan on putting in your Settings class?

answered Nov 17 '13 at 21:42

Bryan Polyak

40
2

To comment, use `add comment` under the question. This area is only for answers. Please delete this post. – Nov 17 '13 at 21:48
1

@Desolator You need a certain amount of reputation in order to post comments. – Nov 17 '13 at 21:49

C++ macro integers and object definitions

3 Answers3