Question

Is there a way to declare a 2D array of integers in two steps? I am having an issue with scope. This is what I am trying to do:

//I know Java, so this is an example of what I am trying to replicate:

int Array[][];
Array = new int[10][10];

Now, in OBJ-C I want to do something similar, but I cant get the syntax right. Right now I have it in one step, but I cannot use it outside of the If-Statement in which I currently have it:

int Array[10][10]; //This is based on an example I found online, but I need 
                   //to define the size on a seperate line than the allocation

Can anyone help me out with this? I know its probably a more basic question, but you can’t use the keyword “new” outside of a message (to my knowledge) and you cant send messages to ints. 🙁

*EDIT 1:**

My problem is scope related.

//Declare Array Somehow
Array[][] //i know this isn't valid, but I need it without size

//if statement
if(condition)
Array[1][2]
else
Array[3][4]

//I need to access it outside of those IFs

//... later in code
Array[0][0] = 5;

Answer 1

This is my preferred way of creating a 2D array, if you know the size of one of the boundaries:

int (*myArray)[dim2];

myArray = calloc(dim1, sizeof(*myArray));

And it can be freed in one call:

free(myArray);

Unfortunately, one of the bounds MUST be fixed for this to work.

However, if you don’t know either of the boundaries, this should work too:

static inline int **create2dArray(int w, int h)
{
    size_t size = sizeof(int) * 2 + w * sizeof(int *);
    int **arr = malloc(size);
    int *sizes = (int *) arr;
    sizes[0] = w;
    sizes[1] = h; 
    arr = (int **) (sizes + 2);

    for (int i = 0; i < w; i++)
    {
        arr[i] = calloc(h, sizeof(**arr));
    }

    return arr;
}

static inline void free2dArray(int **arr)
{
     int *sizes = (int *) arr;
     int w = sizes[-2];
     int h = sizes[-1];

     for (int i = 0; i < w; i++)
         free(arr[i]);

     free(&sizes[-2]);
}