Function to add struct to another struct in C - c

Question

so I have 3 structs here:
typedef struct {
char *name; // allocated
int commonality;
int weight;
} monster;
typedef struct {
char *name; // allocated
char *description; // allocated
double area;
int monsters;
monster **monsters; // allocated
} region;
typedef struct {
char *name; // allocated
double diameter;
int regions;
region **regions; // allocated
} planet;
I already have function:
monster *new_monster(char *name, int commonality, int weight);
I am trying to create these functions:
void add_monster_to_region(region *r, char *mname, int mcommonality, int weight);
void delete_region_from_planet(planet *p, char *rname);
This is what I have so far, but I don't believe it's right, can anyone tell me what I'm doing wrong and how I can fix it?
void add_monster_to_region(region *r, char *mname, int mcommonality, int mweight)
{
for (int i = 0; i < mcommonality; i++)
{
if (strcmp(mname, r->monsters[i]->name) == 0)
{
r->monsters[i]->name = mname;
}
}
}
Thank you

Answer 1

It would be very helpful to have a minimal reproducible example. It would also clarify what was meant with fully allocated NOT a reference array.
Nevertheless, here is my take on how to create a planet, two regions and how to populate the regions with monsters:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct {
char *name; // allocated
int commonality;
int weight;
} monster;
typedef struct {
char *name; // allocated
char *description; // allocated
double area;
int monster_count;
monster **monsters; // fully allocated, NOT a reference array
} region;
typedef struct {
char *name; // allocated
double diameter;
int region_count;
region **regions; // fully allocated, NOT a reference array
} planet;
monster *new_monster(char *name, int commonality, int weight) {
monster *new_monster = calloc(sizeof(monster), 0);
if (new_monster != NULL) {
new_monster->name = strdup(name);
if (new_monster->name == NULL) {
free(new_monster);
return NULL;
}
new_monster->commonality = commonality;
new_monster->weight = weight;
}
return new_monster;
}
void free_monster(monster *the_monster) {
if (the_monster != NULL) {
if (the_monster->name != NULL) {
free(the_monster->name);
}
free(the_monster);
}
}
void add_monster_to_region(region *r, char *mname, int mcommonality, int mweight)
{
monster *a_monster = new_monster(mname, mcommonality, mweight);
if (a_monster == NULL) return; // no memory
monster **monsters = NULL;
if (r->monsters != NULL) {
monsters = realloc(r->monsters, (r->monster_count + 1) * sizeof(monster *));
} else {
monsters = calloc(sizeof(monster *), 0);
}
if (monsters == NULL) {
free_monster(a_monster);
return; // no memory
}
r->monsters = monsters;
r->monsters[r->monster_count] = a_monster;
r->monster_count++;
}
void delete_region_from_planet(planet *p, char *rname) {
// TODO
}
int main() {
region desert = {"Desert", "Sunny and warm place.", 50.0, 0, NULL};
region ocean = {"Ocean", "Huge wet place.", 500.0, 0, NULL};
region *regions[] = {&desert, &ocean};
planet mud = {"Mud", 100.00, 2, regions};
add_monster_to_region(&desert, "Bug", 100, 100);
add_monster_to_region(&desert, "Zombie", 10, 20);
add_monster_to_region(&ocean, "Shark", 20, 40);
for (int i = 0; i < mud.region_count; i++) {
for (int j = 0; j < mud.regions[i]->monster_count; j++) {
printf("%s %d %d\n",
mud.regions[i]->monsters[j]->name,
mud.regions[i]->monsters[j]->commonality,
mud.regions[i]->monsters[j]->weight
);
}
}
// TODO: release allocated memory
return 0;
}
We can see all monsters in all regions of the defined planet:
$ gcc -Wall monsters.c
$ ./a.out
Bug 100 100
Zombie 10 20
Shark 20 40
$