I am trying to change the elements of a C-style array. Using an NSArray/NSMutableArray is not an option for me.
My code is as so:
int losingPositionsX[] = {0, 4, 8...};
but when I enter this code
losingPositionsX = {8, 16, 24};
to change the arrays elements of he array it has an error of: "expected expression" How can I make the copy?
In C (and by extension, in Objective C) you cannot assign C arrays to each other like that. You copy C arrays with memcpy, like this:
int losingPositionsX[] = {0, 4, 8};
memcpy(losingPositionsX, (int[3]){8, 16, 24}, sizeof(losingPositionsX));
Important: this solution requires that the sizes of the two arrays be equal.
sizeof(someNumber) would give you wrong results. If you want to copy someNumber of integers, use sizeof(int)*someNumber.You have to use something like memcpy() or a loop.
#define ARRAY_SIZE 3
const int VALUES[ARRAY_SIZE] = {8, 16, 24};
for (int i = 0; i < ARRAY_SIZE; i++)
losingPositionsX[i] = VALUES[i];
Alternatively, with memcpy(),
// Assuming VALUES has same type and size as losingPositions
memcpy(losingPositionsX, VALUES, sizeof(VALUES));
// Same thing
memcpy(losingPositionsX, VALUES, sizeof(losingPositionsX));
// Same thing (but don't use this one)
memcpy(losingPositionsX, VALUES, sizeof(int) * 3);
Since you are on OS X, which supports C99, you can use compound literals:
memcpy(losingPositionsX, (int[3]){8, 16, 24}, sizeof(losingPositionsX));
The loop is the safest, and will probably be optimized into the same machine code as memcpy() by the compiler. It's relatively easy to make typos with memcpy().
I do not know, whether it is a help for you in relation to memory management. But you can do
int * losingPositionsX = (int[]){ 0, 4, 8 };
losingPositionsX = (int[]){ 8, 16, 32 };
