gistfile1.txt

- (void)swap:(id*)a with:(id*)b
{
    id c = *a;
    *a = *b;
    *b = c;
}

    id a = @1;
    id b = @2;
    
    NSLog(@"a is %@",a);
    NSLog(@"b is %@",b);
    
    [self swap:&a with:&b];
    
    NSLog(@"a is %@",a);
    NSLog(@"b is %@",b);

2013-06-05 23:45:46.548 App[26572:c07] a is 1
2013-06-05 23:45:46.549 App[26572:c07] b is 2
2013-06-05 23:45:46.549 App[26572:c07] a is 2
2013-06-05 23:45:46.549 App[26572:c07] b is 1