Question

Is this a convenient way for swapping two ivar arrays in objective C?

- (void) foo {
    NSArray *aux;
    aux = array1;
    array2 = array1;
    array1 = array2;
}

Are there any alternatives? May it have problems related to retainCount under some circumstances?
I am confused because in the program that I am reviewing the swap is done by:

- (void) foo {
    NSArray *aux;
    aux = array1;
    [aux retain];
    array2 = array1;
    array1 = array2;
    [aux release];
}

Answer 1

In your example, you’re swapping just the pointers. And by the way, you’re doing
it wrong:

- (void) foo {
    NSArray *aux;
    aux = array1;       /* aux is array1 */
    array2 = array1;    /* array2 is array1 */
    array1 = array2;    /* array1 is array1 */
}

If you have properties on those arrays, I’d recommend going with it:

- (void)swapMyArrays
{
    NSArray *temp = [NSArray arrayWithArray:self.array1];
    [self setArray2:array1];
    [self setArray1:temp];
}