enum and struct definition - c

Question

I have errors when compiling my project with codeblocks.
My problem comes from a enum definition, and from a struct definition.
They are bot defined in a header file, that worked since i was only using those enum and struct in the .c associated file. But when i include the .h file in another .c file, i get errors, here is some code;
maps.h
#include <stdlib.h>
#include <stdio.h>
enum Property { BACKGROUND, FOREGROUND, BLOCK, EVENT };
typedef struct {
char map_name[50];
int width;
int height;
char* map_struct;
}rpgMap;
char getTileProperty(rpgMap map, int x, int y, int property);
maps.c
#include "maps.h"
char getTileProperty(rpgMap map, int x, int y, int property){ // Works
char value = NULL;
value = map.map_struct[(((y*(map.width-1))+y+x) * 4 ) + property];
return value;
}
rpgMap loadMap(unsigned char* map){
rpgMap Map;
//....
//some code
//...
return Map;
}
// This works until i include maps.h in another .c file
So here's the stuff, when i include maps.h in eg. game.c or game.h i have this error;
error: nested redefinition of 'enum Property'
I don't get it !

Answer 1

You need to add header guards to your header files otherwise you will get multiple declarations.
For example, for your maps.h surround it with this:
#ifndef MAPS_H
#define MAPS_H
...
#endif

Answer 2

Any source file that includes your header file will declare a single instance variable with the possible enumerated values of { BACKGROUND, FOREGROUND, BLOCK, EVENT }. I'm not sure that this is your intention. In general it is not good practice to do so.
If you intended to declare a type of enumeration and allow instances to be created elsewhere, put this in your header file:
typedef enum { BACKGROUND, FOREGROUND, BLOCK, EVENT } Property_t;
And then in your source files, declare the enumeration like so:
static Property_t property = BACKGROUND;
If you intended to create a variable that can be accessed from multiple source files then do put this in your header file:
typedef enum { BACKGROUND, FOREGROUND, BLOCK, EVENT } Property_t;
extern Property_t property;
and in a single source file, declare the variable:
Property_t property = BACKGROUND;