how do you swap two arrays in obj-c

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 tha开发者_开发知识库t I am reviewing the swap is done by:

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

Neither of them will work, you are not using your aux variable anywhere, at the end they will both point to the same memory location do this instead:

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

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];
}

I think you have a mistake at the end, and it should be:

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

otherwise you make both arrays the same one.

I edited the answer as for the (correct) comments regarding a mistake in the variables I made.