Array in C struct

I want to have two arrays in a struct, which are initialized at start but need editing further on. I need three instances of the struct, so that I can index into a specific struct and modify as I wish. Is it possible?

This is what I thought I could do but I get errors:

struct potNumber{
    int array[20] = {[0 ... 19] = 10};
    char *th开发者_运维问答eName[] = {"Half-and-Half", "Almond", "Rasberry", "Vanilla", …};
} aPot[3];

Then I access the structs as follows:

 printf("some statement %s", aPot[0].array[0]);
 aPot[0].theName[3];
 …

The struct themselves do not have data. You need to create objects of the struct type and set the objects ...

struct potNumber {
    int array[20];
    char *theName[42];
};

/* I like to separate the type definition from the object creation */
struct potNumber aPot[3];
/* with a C99 compiler you can use 'designated initializers' */
struct potNumber bPot = {{[7] = 7, [3] = -12}, {[4] = "four", [6] = "six"}};

for (i = 0; i < 20; i++) {
  aPot[0].array[i] = i;
}
aPot[0].theName[0] = "Half-and-Half";
aPot[0].theName[1] = "Almond";
aPot[0].theName[2] = "Rasberry";
aPot[0].theName[3] = "Vanilla";
/* ... */

for (i = 0; i < 20; i++) {
  aPot[2].array[i] = 42 + i;
}
aPot[2].theName[0] = "Half-and-Half";
aPot[2].theName[1] = "Almond";
aPot[2].theName[2] = "Rasberry";
aPot[2].theName[3] = "Vanilla";
/* ... */

In C struct array elements must have a fixed size, so the char *theNames[] is not valid. Also you can not initialize a struct that way. In C arrays are static, i.e. one cannot change their size dynamically.

A correct declaration of the struct would look like the following

struct potNumber{
    int array[20];
    char theName[10][20];
};

and you initialize it like this:

struct potNumber aPot[3]=
{
    /* 0 */
    { 
        {10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 /* up to 20 integer values*/ },
        {"Half-and-Half", "Almond", "Raspberry", "Vanilla", /* up to 10 strings of max. 20 characters */ }
    },
    /* 1 */
    { 
        {10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 /* up to 20 integer values*/ },
        {"Half-and-Half", "Almond", "Raspberry", "Vanilla", /* up to 10 strings of max. 20 characters */ }
    },
    /* 2 */
    { 
        {10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10 /* up to 20 integer values*/ },
        {"Half-and-Half", "Almond", "Raspberry", "Vanilla", /* up to 10 strings of max. 20 characters */ }
    }
};

But, I'm pretty sure this is not what you want. The sane way to do this required some boilerplate code:

struct IntArray
{
    size_t elements;
    int *data;
};

struct String
{
    size_t length;
    char *data;
};

struct StringArray
{
    size_t elements;
    struct String *data;
};
/* functions for convenient allocation, element access and copying of Arrays and Strings */

struct potNumber
{
    struct IntArray array;
    struct StringArray theNames;
};

Personally I strongly advise against using naked C arrays. Doing everything through helper structs and functions keeps you clear from buffer under/overruns and other trouble. Every serious C coder builds a substancial code library with stuff like this over time.