How do I iterate through an array of structs? - c

Question

I have this hashmap I want to implement.
typedef void * Data;
typedef struct {
Data data; //Data pointer to the data
char * key; //char pointer to the string key
} HashMapItem;
typedef struct hashmap {
HashMapItem * items; //items of the hashmaps
size_t size; //size of the hashmaps
int count; //how many elements are in the hashmap
} HashMap;
I declare it like so:
HashMap * create_hashmap(size_t key_space){
if(key_space == 0)
return NULL;
HashMap * hm = malloc(sizeof(HashMap)); //allocate memory to store hashmap
hm->items = calloc(key_space, sizeof(HashMapItem)); //allocate memory to store every item inside the map, null it
hm->size = key_space; //set sitze of hashmap
hm->count = 0; //empty at the begining
return hm;
}
When i try to iterate through it, it says that
expression must have arithmetic or pointer type but has type "HashMapItem" even though i declare it as a pointer of HashMapItems
if((hm->items)[index] != NULL)
Any idea?

Answer 1

typedef void * Data;
Never hide pointers behind typedefs. It is a very, very bad practice.
How to iterate.
typedef struct {
void *data; //Data pointer to the data
char * key; //char pointer to the string key
} HashMapItem;
typedef struct hashmap {
HashMapItem * items; //items of the hashmaps
size_t size; //size of the hashmaps
size_t count; //how many elements are in the hashmap
} HashMap;
void foo(HashMap *map)
{
for(size_t i = 0; i < map -> count; i ++)
{
puts(map -> items[i].key);
}
}
PS count member should be also size_t
EDIT. Below is wrong as hm->items)[index] has type HashMapItem and it is not pointer. You cant compare it to NULL.
if((hm->items)[index] != NULL)